Declare plugin settings in the manifest, resolve them from the environment

examples/plugins/admin/i18n/en-US.ts

@@ -83,9 +83,29 @@ const messages = {
 
   "admin.nav.clients": "OAuth2 clients",
   "admin.nav.groups": "Groups",
+  "admin.nav.pluginSettings": "Plugin settings",
   "admin.nav.section": "Admin",
   "admin.nav.users": "Users",
 
+  "admin.pluginSettings.caption": "Settings declared by {{plugin}}",
+  "admin.pluginSettings.column.description": "Description",
+  "admin.pluginSettings.column.key": "Key",
+  "admin.pluginSettings.column.required": "Required",
+  "admin.pluginSettings.column.source": "Source",
+  "admin.pluginSettings.column.type": "Type",
+  "admin.pluginSettings.column.value": "Value",
+  "admin.pluginSettings.column.variable": "Variable",
+  "admin.pluginSettings.no": "No",
+  "admin.pluginSettings.none": "This plugin declares no settings.",
+  "admin.pluginSettings.secretSet": "Secret — set",
+  "admin.pluginSettings.secretUnset": "Secret — not set",
+  "admin.pluginSettings.source.default": "Default",
+  "admin.pluginSettings.source.env": "Environment",
+  "admin.pluginSettings.source.unset": "Not set",
+  "admin.pluginSettings.title": "Plugin settings",
+  "admin.pluginSettings.unset": "—",
+  "admin.pluginSettings.yes": "Yes",
+
   "admin.notFound.message": "That item doesn't exist.",
   "admin.notFound.title": "Not found",