[#4393] added Planning Center OAuth2 provider

Co-authored-by: alxjsn <alxjsn@sameorigin.org>

ui/src/providers.js

@@ -128,6 +128,11 @@ export default [
         optionsComponent: SelfHostedOptions,
         optionsComponentProps: { required: true },
     },
+    {
+        key:   "planningcenterAuth",
+        title: "Planning Center",
+        logo:  "planningcenter.svg",
+    },
     {
         key:   "oidcAuth",
         title: "OpenID Connect",