GH-4: Add brief descriptions for each section

Author: ArtyomVancyan

README.md

@@ -1,6 +1,7 @@
 # fastapi-oauth2 <img src="https://github.com/pysnippet.png" align="right" height="64" />
 
-[//]: # (TODO: LONG DESCRIPTION)
+FastAPI OAuth2 is a middleware-based social authentication mechanism supporting several auth providers. It depends on
+the [social-core](https://github.com/python-social-auth/social-core) authentication backends.
 
 ## Features to be implemented
 
@@ -17,15 +18,36 @@ python -m pip install fastapi-oauth2
 
 ## Configuration
 
-[//]: # (TODO: LONG DESCRIPTION)
+Configuration requires you to provide the JWT requisites and define the clients of the particular providers. The
+middleware configuration is declared with the `OAuth2Config` and `OAuth2Client` classes.
+
+### OAuth2Config
+
+- `allow_http` - Allow insecure HTTP requests. Defaults to `False`.
+- `jwt_secret` - The secret key used to sign the JWT. Defaults to `None`.
+- `jwt_expires` - The expiration time of the JWT in seconds. Defaults to `900`.
+- `jwt_algorithm` - The algorithm used to sign the JWT. Defaults to `HS256`.
+- `clients` - The list of the OAuth2 clients. Defaults to `[]`.
+
+### OAuth2Client
+
+- `backend` - The [social-core](https://github.com/python-social-auth/social-core) authentication backend classname.
+- `client_id` - The OAuth2 client ID for the particular provider.
+- `client_secret` - The OAuth2 client secret for the particular provider.
+- `redirect_uri` - The OAuth2 redirect URI to redirect to after success. Defaults to the base URL.
+- `scope` - The OAuth2 scope for the particular provider. Defaults to `[]`.
+
+It is also important to mention that for the configured clients of the auth providers, the authorization URLs are
+accessible by the `/oauth2/{provider}/auth` path where the `provider` variable represents the exact value of the auth
+provider backend `name` attribute.
 
 ```python
 from fastapi_oauth2.client import OAuth2Client
 from fastapi_oauth2.config import OAuth2Config
 from social_core.backends.github import GithubOAuth2
 
 oauth2_config = OAuth2Config(
-    allow_http=True,
+    allow_http=False,
     jwt_secret=os.getenv("JWT_SECRET"),
     jwt_expires=os.getenv("JWT_EXPIRES"),
     jwt_algorithm=os.getenv("JWT_ALGORITHM"),
@@ -34,25 +56,30 @@ oauth2_config = OAuth2Config(
             backend=GithubOAuth2,
             client_id=os.getenv("OAUTH2_CLIENT_ID"),
             client_secret=os.getenv("OAUTH2_CLIENT_SECRET"),
+            redirect_uri="https://pysnippet.org/",
             scope=["user:email"],
         ),
     ]
 )
 ```
 
-## Usage
+## Integration
 
-[//]: # (TODO: LONG DESCRIPTION)
+To integrate the package into your FastAPI application, you need to add the `OAuth2Middleware` with particular configs
+in the above-represented format and include the router to the main router of the application.
 
 ```python
 from fastapi import FastAPI
 from fastapi_oauth2.middleware import OAuth2Middleware
+from fastapi_oauth2.router import router as oauth2_router
 
 app = FastAPI()
+app.include_router(oauth2_router)
 app.add_middleware(OAuth2Middleware, config=oauth2_config)
 ```
 
-[//]: # (TODO: LONG DESCRIPTION)
+After adding the middleware, the `user` attribute will be available in the request context. It will contain the user
+data provided by the OAuth2 provider.
 
 ```jinja2
 {% if request.user.is_authenticated %}