add README and modify payer scope handling of 'initialize_state'

README.md

@@ -0,0 +1,55 @@
+# patient-access-api
+A lightweight backend server with handlers to:
+1. Perform oauth2 pkce authorization flow
+2. Implements redirection to authenticate a user with a payer's application and access token trading.
+3. Basic requests to query data for the authenticated user.
+
+## Dependencies
+- Register as a developer with a Payer (e.g. developer.cigna.com)
+- Sign up for an ngrok account to get a custom subdomain name
+
+## Usage
+Populate a `config.toml`, using the following template:
+```toml
+[cigna_sandbox]
+client_id=""
+token_url=""
+auth_url=""
+api_scopes=["write", "read"]
+redirect_url="<the callback url you registered with cigna>"
+
+[cigna_prod]
+[cigna_sandbox]
+client_id=""
+token_url=""
+auth_url=""
+api_scopes=["write", "read"]
+redirect_url="<the callback url you registered with cigna>"
+
+[ngrok_config]
+auth_token=""
+tunnel_url="<your custom ngrok url>"
+```
+Build :
+```bash
+cargo build --release
+```
+Execute to launch the server:
+
+```bash
+$ target/release/patient_access_api --config <path-to-your-config.toml>
+```
+
+If successfully launched you should see:
+```
+2023-06-03T16:40:51.754303Z  INFO patient_access_api::settings: Configuring Payer Environment to: <payer-environment>
+2023-06-03T16:40:52.728791Z  INFO patient_access_api: Starting Server...
+2023-06-03T16:40:52.728865Z  INFO patient_access_api: Serving on <ngrok-tunnel-url>
+```
+For help:
+```
+$ patient_access_api --help
+```
+
+If the server is successfully launched, visit `<ngrok-tunnel-url>`.  
+To trigger a patient authentication go to: `<ngrok-tunnel-url>/authz`