Log complete token validation error only to debug log (#14674)

* Log complete token validation error only to debug log

Logging e's stack trace causes _thousands_ of extra noisy log lines,
even for relatively benign causes, like tokens expiring. The noise makes
it difficult to see what actually wrong.

* Add colon before exception message

src/metabase/public_settings/metastore.clj

@@ -144,7 +144,8 @@
     (or (some-> (premium-embedding-token) valid-token->features)
         #{})
     (catch Throwable e
-      (log/error e (trs "Error validating token"))
+      (log/error (trs "Error validating token") ":" (ex-message e))
+      (log/debug e (trs "Error validating token"))
       #{})))
 
 (defsetting hide-embed-branding?