fix(log): Log error conditions in the server logs

An error that indicates incorrect configuration, set up, or otherwise something an
administrator would probably want to know, should also be logged to the server logs.
Those log messages should including enough information for an administrator to find the
specific instance of the issue (e.g. which Plone portal in a multi-portal ZODB).

src/plone/restapi/services/auth/login.py

@@ -7,8 +7,11 @@
 from zope.interface import alsoProvides
 from zope import component
 
+import logging
 import plone.protect.interfaces
 
+logger = logging.getLogger(__name__)
+
 
 class Login(Service):
     """Handles login and returns a JSON web token (JWT)."""
@@ -45,10 +48,16 @@ def reply(self):
 
             if plugin is None:
                 self.request.response.setStatus(501)
+                message = "JWT authentication plugin not installed"
+                logger.error(
+                    "%s: %s",
+                    message,
+                    "/".join(uf.getPhysicalPath()),
+                )
                 return dict(
                     error=dict(
                         type="Login failed",
-                        message="JWT authentication plugin not installed.",
+                        message=message,
                     )
                 )