Add authentication from upstream providers (#107)

Let BasicOIDC delegate authentication to upstream providers (Google, GitHub, GitLab, Keycloak...)

Reviewed-on: #107

src/constants.rs

@@ -6,6 +6,9 @@ pub const USERS_LIST_FILE: &str = "users.json";
 /// File in storage containing clients list
 pub const CLIENTS_LIST_FILE: &str = "clients.yaml";
 
+/// File in storage containing providers list
+pub const PROVIDERS_LIST_FILE: &str = "providers.yaml";
+
 /// Default built-in credentials
 pub const DEFAULT_ADMIN_USERNAME: &str = "admin";
 pub const DEFAULT_ADMIN_PASSWORD: &str = "admin";
@@ -68,3 +71,15 @@ pub const OPEN_ID_REFRESH_TOKEN_TIMEOUT: u64 = 360000;
 /// Webauthn constants
 pub const WEBAUTHN_REGISTER_CHALLENGE_EXPIRE: u64 = 3600;
 pub const WEBAUTHN_LOGIN_CHALLENGE_EXPIRE: u64 = 3600;
+
+/// OpenID providers login state constants
+pub const OIDC_STATES_CLEANUP_INTERVAL: Duration = Duration::from_secs(60);
+pub const MAX_OIDC_PROVIDERS_STATES: usize = 10;
+pub const OIDC_PROVIDERS_STATE_LEN: usize = 40;
+pub const OIDC_PROVIDERS_STATE_DURATION: u64 = 60 * 15;
+
+/// OpenID providers configuration constants
+pub const OIDC_PROVIDERS_LIFETIME: u64 = 3600;
+
+/// OpenID provider callback URI
+pub const OIDC_PROVIDER_CB_URI: &str = "/prov_cb";