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 (metadata1.clusterUUID.equals(metadata2.clusterUUID) == false) {
            return false;
        }
        if (metadata1.clusterUUIDCommitted != metadata2.clusterUUIDCommitted) {
            return false;
        }
        
        int customCount1 = 0;
        for (Map.Entry<String, Custom> cursor : metadata1.customs.entrySet()) {
            if (cursor.getValue().context().contains(XContentContext.GATEWAY)) {
                if (cursor.getValue().equals(metadata2.custom(cursor.getKey())) == false) {
                    return false;
                }
                customCount1++;
            }
        }
        int customCount2 = 0;
        for (Custom custom : metadata2.customs.values()) {
            if (custom.context().contains(XContentContext.GATEWAY)) {
                customCount2++;
            }
        }
        if (customCount1 != customCount2) {
            return false;
        }
        if (Objects.equals(metadata1.reservedStateMetadata, metadata2.reservedStateMetadata) == false) {
            return false;
        }
        return true;