refactor: rework scheme validation in oauth controller and frontend (#1026)

internal/controller/oauth_controller_test.go

@@ -81,14 +81,6 @@ func TestOAuthController_isRedirectSafe(t *testing.T) {
 			redirectURI:       "https://sub.example.com",
 			expected:          false,
 		},
-		{
-			description:       "Different scheme returns false",
-			appURL:            "https://tinyauth.example.com",
-			cookieDomain:      "example.com",
-			subdomainsEnabled: true,
-			redirectURI:       "http://tinyauth.example.com",
-			expected:          false,
-		},
 		{
 			description:       "Different port returns false",
 			appURL:            "https://tinyauth.example.com",