docs: adding content for module 3

100-level-AsyncAPI-Intro/step2.md

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+As Eve and Chan begin building a communication system using AsyncAPI inside Chan's spaceship control room, Chan asks Eve if there is a standardized way of defining the communication system or if she defines the communication systems differently based on the particular use case.
+
+Eve replies that AsyncAPI has a standardized way of defining communication systems. She explains to Chan that the communication system is defined using a specific structure within an AsyncAPI document. As it is much easier to understand things in action, Eve shows Chan how to structure components in an AsyncAPI document.
+
+## Understanding AsyncAPI components 
+
+- **Info**
+
+Just as the name tag on Chan's spaceship provides essential details like the spaceship's name and model, the `info` section in AsyncAPI serves a similar purpose. It provides crucial information about the API, such as the title, version, and description. The `info` metadata helps developers understand the basic API details they're working with.
+
+```yml
+asyncapi: '3.0.0'
+info:
+  title: Space Communication API
+  version: '1.0.0'
+  description: API for communication between Chan's spaceship and Capuccinova
+```
+
+- **Servers**
+
+Imagine that Chan's spaceship communicates with Eve on Capuccinova through various servers.  In AsyncAPI, the `servers` section serves to describe both the servers that the application of the API communicates with and the servers that the application itself exposes, such as a websocket interface or HTTP Rest.
+
+```yml
+servers:
+  production:
+    host: mqtt://localhost
+    protocol: mqtt
+    description: Production server for space communication
+```
+
+- **Channels**
+
+The spaceship's radio stations, which correspond to specific topics like communicating with Capuccinova, are similar to the `channels` in AsyncAPI. These channels represent paths for sending specific types of messages. Each channel uses an address, which is a template for the URL of the server, and can have parameters inside curly braces that can be replaced dynamically at runtime.
+
+```yml
+channels:
+  chatRoom:
+    address: chat
+    messages:
+      chatMessage:
+        name: ChatMessage
+        payload:
+          type: object
+          properties:
+            userId:
+              type: string
+              description: The ID of the user who sent the message
+            message:
+              type: string
+              description: The chat message
+            spacename:
+              type: string
+              description: The unique spacename identifier for the message
+```
+
+
+## Operations, messages, and schemas
+
+- **Operations**
+
+`Operations` in AsyncAPI are like the instructions for the spaceship. They define what actions can be performed within each channel, such as sending or receiving messages. Each operation is associated with a channel and its messages.
+
+```yml
+operations:
+  sendChatMessage:
+    action: 'send'
+    summary: Send a chat message to a specific room
+    channel:
+      $ref: '#/channels/roomidchat'
+```
+
+- **Messages**
+
+`Messages` in AsyncAPI are the content exchanged during operations, just like the words Eve from Capuccinova and Chan from Brownieterra use to communicate. They describe the structure and content of the messages sent or received.
+
+
+```yml
+components:
+  messages:
+    ChatMessage:
+      contentType: application/json
+      payload:
+        $ref: '#/components/schemas/ChatMessagePayload'
+```
+
+- **Schemas**
+
+`Schemas` in AsyncAPI are like the blueprints for the spaceship. They allows the definition of input and output data types.
+
+```yml
+components:
+  schemas:
+    ChatMessagePayload:
+      type: object
+      properties:
+        userId:
+          type: string
+          description: The ID of the user who sent the message
+        message:
+          type: string
+          description: The chat message
+```
+
+- **Components**
+
+`Component` is like the toolbox in Chan's spaceship. It contains a set of reusable objects for different aspects of the AsyncAPI specification. All objects defined within the components object will have no effect on the API unless they are explicitly referenced from properties outside the components object.
+
+```yml
+components:
+  messages:
+    ChatMessage:
+      name: ChatMessage
+      title: Chat Message
+      contentType: application/json
+      payload:
+        $ref: '#/components/schemas/ChatMessagePayload'
+  schemas:
+    ChatMessagePayload:
+      type: object
+      properties:
+        userId:
+          type: string
+          description: The ID of the user who sent the message
+        message:
+          type: string
+          description: The chat message
+## Request/reply 
+As Eve and Chan near the completion of their communication system setup, Eve takes a moment to elaborate on the request/reply pattern to Chan, emphasizing that it is a communication pattern rather than a separate component.
+
+Eve clarifies to Chan that this pattern involves two key roles: a requestor and a replier.
+
+In their setup, they establish a channel named `communication` to facilitate requests and enable communication. Now they can stay in touch and communicate about Eve's adventures and Chan's fascinating discoveries during his intergalactic travels. 
+
+```yml
+asyncapi: 3.0.0
+info:
+  title: Eve And Chan's Communication APP
+  version: 1.0.0
+channels:
+  communication:
+    address: /brownieterra
+    messages:
+      chit_chat:
+        payload:
+          type: string
+      cool_discovery:
+        payload:
+          type: object
+          properties:
+            title:
+              type: string
+            info:
+              type: string
+            date:
+              type: string
+      confirmation:
+        payload:
+          type: boolean
+operations:
+  sendChit_Chat:
+    action: send
+    channel:
+      $ref: "#/channels/communication"
+    messages:
+      - $ref: "#/channels/communication/messages/chit_chat"
+    reply:
+      channel:
+        "$ref": '#/channels/communication'
+      messages:
+       - $ref: "#/channels/communication/messages/chit_chat"
+  sendDiscovery:
+    action: send
+    channel:
+      $ref: "#/channels/communication"
+    messages:
+      - $ref: "#/channels/communication/messages/cool_discovery"
+    reply:
+      channel:
+        "$ref": '#/channels/communication'
+      messages:
+       - $ref: "#/channels/communication/messages/confirmation"
+```
+
+Chan wonders how Eve could reach him if he travels around and his address(reply address) is unknown. 
+
+Eve teaches Chan how to set up a communication system and stay in touch even when the reply address is not known. 
+
+```yaml 
+channels:
+  communication:
+    address: /brownieterra
+    messages:
+      chit_chat:
+        payload:
+          type: string
+      cool_discovery:
+        payload:
+          type: object
+          properties:
+            title:
+              type: string
+            info:
+              type: string
+            date:
+              type: string
+      confirmation:
+        payload:
+          type: boolean
+  secret_channel:
+    address: /cappucinova
+    messages:
+      secret_stuff:
+        payload:
+          type: string
+operations:
+  sendSecretMessage:
+    action: send
+    channel:
+      "$ref": "#/channels/secret_channel"
+    reply:
+      address:
+        "description": "Consumer inbox"
+        "location": "$message.header#/secret_reply_channel"
+  sendChit_Chat:
+    action: send
+    channel:
+      $ref: "#/channels/communication"
+    messages:
+      - $ref: "#/channels/communication/messages/chit_chat"
+    reply:
+      channel:
+        "$ref": '#/channels/communication'
+      messages:
+       - $ref: "#/channels/communication/messages/chit_chat"
+  sendDiscovery:
+    action: send
+    channel:
+      $ref: "#/channels/communication"
+    messages:
+      - $ref: "#/channels/communication/messages/cool_discovery"
+    reply:
+      channel:
+        "$ref": '#/channels/communication'
+      messages:
+       - $ref: "#/channels/communication/messages/confirmation"
+```
+
+With the final pieces programmed and the communication system in place, Chan gets ready to return home. 
+
+Making a promise to stay in touch, Chan takes off in his spaceship back to Brownieterra.