homed: return a better error when a home has no authentication information defined

We can't log into home entries that have no password or PKCS#11 token.
Return a proper, useful error in that case.

See: #15178

src/home/homed-home.c

@@ -471,6 +471,8 @@ static int convert_worker_errno(Home *h, int e, sd_bus_error *error) {
                 return sd_bus_error_setf(error, BUS_ERROR_HOME_NOT_ACTIVE, "Home %s is currently not active", h->user_name);
         case -ENOSPC:
                 return sd_bus_error_setf(error, BUS_ERROR_NO_DISK_SPACE, "Not enough disk space for home %s", h->user_name);
+        case -EKEYREVOKED:
+                return sd_bus_error_setf(error, BUS_ERROR_HOME_CANT_AUTHENTICATE, "Home %s has no password or other authentication mechanism defined.", h->user_name);
         }
 
         return 0;

src/home/homework.c

@@ -1489,6 +1489,7 @@ static int run(int argc, char *argv[]) {
          * EBUSY           → file system is currently active
          * ENOEXEC         → file system is currently not active
          * ENOSPC          → not enough disk space for operation
+         * EKEYREVOKED     → user record has not suitable hashed password or pkcs#11 entry, we cannot authenticate
          */
 
         if (streq(argv[1], "activate"))