Merge pull request #30 from Peersyst/docs/feat/concepts-authentication

[TA-4995]: concepts/authentication page

Author: AdriaCarrera

docs/docs/concepts/architecture_custom_backend.md

@@ -1,7 +1,22 @@
 # Custom backend
 
-:::caution
+When integrating FastAuth, you can choose to use a custom backend to handle the authentication and authorization of the user. This is useful if you want to use a different authentication provider or if you want to use a different authorization model.
 
-This page is under construction.
+:::warning
+
+Implementing a custom backend may require additional development and maintenance, as you will need to implement the authentication and authorization logic for your specific use case.
 
 :::
+
+## Aspects to consider
+
+When implementing a custom backend, there are several aspects to consider:
+
+- **Custom authentication**: You will need to implement the authentication logic for your specific use case. This may include implementing a login page, a logout page, and a user profile page. In addition, you will need to implement the logic to verify the user's identity and ensure the transaction or delegated action is authorized.
+- **Security**: You will need to ensure that no keys or secrets are exposed to the client. This is important to prevent unauthorized access to your resources.
+
+## Example
+
+If you want to integrate a custom backend, you can follow this [integration guide](../integrations/custom-backend.md). It will guide you through the process of integrating a custom backend with FastAuth.
+
+If you are looking for an example of a custom backend, you can check out the [Express](../integrations/custom-backend-express.md) example. It shows how to develop a custom backend using [Express.js](https://expressjs.com/), taking care of the authentication and authorization logic.

docs/docs/concepts/auth0.md

@@ -1,7 +1,27 @@
 # Auth0
 
-:::caution
+FastAuth leverages [Auth0](https://auth0.com/) as its **primary authentication provider**, enabling a seamless and secure social login experience for users. Auth0 provides a robust identity platform that handles user authentication across multiple providers while maintaining high security standards.
 
-This page is under construction.
+:::info
+
+This authentication method is the default and is used for all transactions and delegated actions by the user. We recommend using this method for the best user experience.
 
 :::
+
+## Supported Login Providers
+
+FastAuth supports several login methods through Auth0:
+
+- **Google**: Users can sign in using their Google accounts, providing a familiar and convenient authentication method. This integration allows users to leverage their existing Google credentials without creating new accounts.
+
+- **Apple**: Apple Sign-In support ensures iOS users can authenticate securely using their Apple ID. This method provides enhanced privacy features and follows Apple's authentication guidelines.
+
+- **Auth0 Username/Password**: Auth0's native username and password authentication system provides a traditional login option for users who prefer to create dedicated accounts.
+
+- **Passkeys**: Support for passkeys offers a modern, passwordless authentication method that enhances security while simplifying the login experience. Passkeys use public key cryptography to authenticate users across their devices.
+
+## Transaction Authentication
+
+For enhanced security, FastAuth requires authentication through Auth0 for every transaction or delegated action by the user. This ensures that all sensitive operations are properly authorized and authenticated, maintaining a secure environment for users' assets and actions.
+
+Transactions and delegated actions are included in the JWT payload returned by Auth0, which is then verified against the [Auth0Guard](./architecture_contracts_auth0-guard.md) contract, verifying the user's identity and ensuring the transaction is authorized.

docs/docs/concepts/getting-started.md

@@ -6,7 +6,7 @@ FastAuth is a NEAR Protocol authentication system that enables secure transactio
 
 1. Review the [Architecture Overview](./architecture_overview.md)
 2. Explore the [Contracts](./architecture_contracts_overview.md)
-3. Choose your authentication method
+3. Choose your [Authentication method](./auth0.md)
 
 ## Learn More