Add Telegram OAuth / OpenID Connect support for Authentication

[noloverme]

Telegram has recently launched native OpenID Connect (OIDC) support alongside their legacy widget. Adding Telegram as a social authentication provider will allow users to log in seamlessy using their Telegram accounts with standard PKCE and Authorization Code Flow.

Implementation Details

Telegram's OIDC implementation supports standard OAuth 2.0 / OpenID Connect specifications:

• Discovery URL: https://oauth.telegram.org/.well-known/openid-configuration
• Authorization Endpoint: https://oauth.telegram.org/auth
• Token Endpoint: https://oauth.telegram.org/token
• JWKS Endpoint: https://oauth.telegram.org/.well-known/jwks.json
• Flow: Authorization Code Flow with PKCE (S256)
• Supported Scopes: openid, profile, phone, telegram:bot_access

Benefits

1. Seamless Login: Single-tap login for millions of Telegram users.
2. Standardized Protocol: Since Telegram now complies with OIDC standards, it seamlessly fits into existing OAuth/Socialite integration architecture without requiring custom script-heavy widgets.
3. Identity Verification: Provides cryptographically signed JWT id_token with basic profile claims (id, name, preferred_username, picture).

doc: https://core.telegram.org/widgets/login
https://core.telegram.org/api/url-authorization

[Boy132]

We won't add more default providers. Additional providers can be added via plugins, as long as Socialite supports them.