Add OIDC login support for Google and Microsoft providers

Implements OpenID Connect authentication flow with PKCE, JWT verification, and enterprise-only account restrictions. Adds OIDC service with JWKS caching and state management, HTTP handlers for login/callback flows, GraphQL query for available providers, and sign-in UI integration.

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

pkg/coredata/session.go

@@ -57,6 +57,8 @@ const (
 	AuthMethodMagicLink AuthMethod = "MAGIC_LINK"
 	AuthMethodPassword  AuthMethod = "PASSWORD"
 	AuthMethodSAML      AuthMethod = "SAML"
+	AuthMethodGoogle    AuthMethod = "GOOGLE"
+	AuthMethodMicrosoft AuthMethod = "MICROSOFT"
 )
 
 func NewRootSession(identityID gid.GID, method AuthMethod, duration time.Duration) *Session {