fix(logging): reduce log level of errors in introspection and login UI (#8047)

# Which Problems Are Solved

Introspection errors such as invalid audience and errors in the login UI
such as invalid user agents where all logged as severity error.

# How the Problems Are Solved

Log level for both general loggers is changed to `info`.

# Additional Changes

None

# Additional Context

- internal discussion

internal/api/oidc/introspect.go

@@ -80,7 +80,11 @@ func (s *Server) Introspect(ctx context.Context, r *op.Request[op.IntrospectionR
 	// with active: false
 	defer func() {
 		if err != nil {
-			s.getLogger(ctx).ErrorContext(ctx, "oidc introspection", "err", err)
+			if zerrors.IsInternal(err) {
+				s.getLogger(ctx).ErrorContext(ctx, "oidc introspection", "err", err)
+			} else {
+				s.getLogger(ctx).InfoContext(ctx, "oidc introspection", "err", err)
+			}
 			resp, err = op.NewResponse(new(oidc.IntrospectionResponse)), nil
 		}
 	}()