feat(auth): add option to disable built-in login when using OIDC (#1908)

* feat(auth): disable built-in login by config

* cleanup config

* fix(web): prevent login form flash by waiting for OIDC config

* refactor(config): standardize OIDC TOML format

- Adds camelCase TOML tags to OIDC config struct while keeping mapstructure tags for backward compatibility
- Updates config template to use camelCase format

* refactor: kyles changes

* refactor: prefix disablebuiltinlogin with oidc

* docs: revert format change

---------

Co-authored-by: ze0s <43699394+zze0s@users.noreply.github.com>

internal/config/config.go

@@ -112,19 +112,22 @@ sessionSecret = "{{ .sessionSecret }}"
 # OpenID Connect Configuration
 #
 # Enable OIDC authentication
-#oidc_enabled = false
+#oidcEnabled = false
 #
 # OIDC Issuer URL (e.g. https://auth.example.com)
-#oidc_issuer = ""
+#oidcIssuer = ""
 #
 # OIDC Client ID
-#oidc_client_id = ""
+#oidcClientId = ""
 #
 # OIDC Client Secret
-#oidc_client_secret = ""
+#oidcClientSecret = ""
 #
 # OIDC Redirect URL (e.g. http://localhost:7474/api/auth/oidc/callback)
-#oidc_redirect_url = ""
+#oidcRedirectUrl = ""
+#
+# Disable Built In Login Form (only works when using external auth)
+#oidcDisableBuiltInLogin = false
 
 # Metrics
 #
@@ -432,6 +435,10 @@ func (c *AppConfig) loadFromEnv() {
 		c.Config.OIDCRedirectURL = v
 	}
 
+	if v := os.Getenv(prefix + "OIDC_DISABLE_BUILT_IN_LOGIN"); v != "" {
+		c.Config.OIDCDisableBuiltInLogin = strings.EqualFold(strings.ToLower(v), "true")
+	}
+
 	if v := os.Getenv(prefix + "METRICS_ENABLED"); v != "" {
 		c.Config.MetricsEnabled = strings.EqualFold(strings.ToLower(v), "true")
 	}