Add support for Field-Level Descriptions

  - Terraform Plugin SDK v2 Upgrade Guide: The helper/schema.Resource and helper/schema.Schema types both now have Description properties that accept strings. These properties are laying the groundwork for future improvements to Terraform, and will have no visible effect to the Terraform CLI at the moment. If you’d like to build in support for your provider starting now, it’s recommended that you set these properties to whatever you’d document the resource or field as in your terraform.io docs for the resource. You can globally set the format of the text in these fields by setting the global variable helper/schema.DescriptionKind. Its acceptable values are helper/schema.StringPlain (plain text, the default) or helper/schema.StringMarkdown (markdown formatting).
    https://www.terraform.io/docs/extend/guides/v2-upgrade-guide.html#support-for-resource-level-and-field-level-descriptions

docs/how_to.md

@@ -1004,6 +1004,7 @@ The following is a list of attributes that can be added to each property to defi
 Attribute Name | Type | Description
 ---|:---:|---
 readOnly | boolean |  A property with this attribute enabled will be considered a computed property. readOnly properties are included in responses but not in requests. Hence, it will not be expected from the consumer of the API when posting the resource. However; it will be expected that the API will return tthe property with the computed value in the response payload.
+description | string | A description for property. 
 default | primitive (int, bool, string) | Documents what will be the default value generated by the API for the given property
 x-terraform-immutable | boolean |  The field will be used to create a brand new resource; however it can not be updated. Attempts to update this value will result into terraform aborting the update. This applies also to properties of type object and also list of objects. If an object property contains this attribute, any update to its child properties will result  terraform aborting the update too. Also, if an object property is does not contain this flag, but any of its child properties, the same principle applies and updates to the values of those properties will not be allowed.
 x-terraform-force-new | boolean |  If the value of this property is updated; terraform will delete the previously created resource and create a new one with this value
@@ -1097,6 +1098,7 @@ definitions:
     properties:
       id: # the value of this computed property is not known at plan time (e,g: uuid, etc)
         type: string
+        description: "some description for the property..."
         readOnly: true
 
       mandatory_property: # this property is required

docs/major_version_release_notes/openapi_terraform_provider_v1.0.0.md

@@ -116,7 +116,45 @@ As part of the update of the CRUD functions to support better diagnosis via the
 upgrade guide, the OpenAPI Terraform provider now supports timeouts not only for async resource operations but also synchronous. The timeouts can
 be specified in the OpenAPI document per resource operation using the [x-terraform-resource-timeout](https://github.com/dikhan/terraform-provider-openapi/blob/master/docs/how_to.md#xTerraformResourceTimeout)
 extension.
-
+
+### Support for Field-Level Descriptions
+
+The [Terraform helper/schema.Schema](https://www.terraform.io/docs/extend/guides/v2-upgrade-guide.html#support-for-resource-level-and-field-level-descriptions) for OpenAPI Terraform 
+compatible resources and data sources now contains a field Description which is populated based on the corresponding OpenAPI definition property's description. 
+
+For instance, the following OpenAPI object definition would be translated into the below helper/schema.Schema
+containing the `property_with_description` and its corresponding description as specified in the OpenAPI document.
+
+```yml
+definitions:
+  ContentDeliveryNetworkV1:
+    type: object
+    properties:
+      ...
+      property_with_description: 
+        type: string
+        description: "some description for the property..."
+      ... 
+```
+
+````
+&schema.Resource{
+        # This will be the Terraform schema of the resource using the ContentDeliveryNetworkV1 model definition
+		Schema: map[string]*schema.Schema {
+		    ...
+		    "property_with_description": *schema.Schema {
+                Type:TypeString 
+                Description: "some description" 
+                Optional:true 
+                Required:false
+                ...		    
+		    }
+		},
+		...
+	}
+````
+
+
 ### To be removed
 
 - Multi-region on resource name level

openapi/openapi_spec_resource_schema_definition_property.go

@@ -221,6 +221,7 @@ func (s *SpecSchemaDefinitionProperty) terraformSchema() (*schema.Schema, error)
 		return nil, err
 	}
 	terraformSchema.Type = schemaType
+	terraformSchema.Description = s.Description
 
 	// complex data structures
 	switch s.Type {

openapi/openapi_spec_resource_schema_definition_property_test.go

@@ -1162,6 +1162,21 @@ func TestTerraformSchema(t *testing.T) {
 		})
 	})
 
+	Convey("Given a swagger schema definition that has a property with a description", t, func() {
+		s := &SpecSchemaDefinitionProperty{
+			Name:        "string_prop",
+			Type:        TypeString,
+			Description: "string_prop description",
+		}
+		Convey("When terraformSchema method is called", func() {
+			tfPropSchema, err := s.terraformSchema()
+			Convey("Then the resulted terraform property schema should contain the description too", func() {
+				So(err, ShouldBeNil)
+				So(tfPropSchema.Description, ShouldEqual, s.Description)
+			})
+		})
+	})
+
 	Convey("Given a swagger schema definition that has a property of type 'array' and the elems are type string", t, func() {
 		s := &SpecSchemaDefinitionProperty{
 			Name:           "array_prop",