A composable index template with no `template` defined in the body is mistakingly always assumed to not be a time series template. Even if it refers to a component template that has the `index.mode` setting set to `time_series` and the component template defines mappings with dimension fields or routing paths.

Incorrectly this causes to create a data stream with a tsdb index *without* time series start and end time settings set. The fact that this can happen is another bug and is being tracked #98833.

What should happen in this case is that a tsdb data stream is created with a valid tsdb backing index (with correctly generated time series start and end time settings).

This bug was found as part investigating #98792 and is the cause of that bug.
server/src/main/java/org/elasticsearch/cluster/metadata/Metadata.java
}
            if (previous.isHidden() != current.isHidden()) {
                return true;
            }
            if (previous.isSystem() != current.isSystem()) {
                return true;
            }
            if (previous.getState() != current.getState()) {
                return true;
            }
            return false;
        }
        public IndexMetadata get(String index) {
            return indices.get(index);
        }
        public IndexMetadata getSafe(Index index) {
            IndexMetadata indexMetadata = get(index.getName());
            if (indexMetadata != null) {
                if (indexMetadata.getIndexUUID().equals(index.getUUID())) {
                    return indexMetadata;
                }
                throw new IndexNotFoundException(
                    index,
                    new IllegalStateException(
                        "index uuid doesn't match expected: [" + index.getUUID() + "] but got: [" + indexMetadata.getIndexUUID() + "]"
                    )
                );
            }
            throw new IndexNotFoundException(index);
        }