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
return builder.build();
        }
        /**
         * Dedupes {@link MappingMetadata} instance from the provided indexMetadata parameter using the sha256
         * hash from the compressed source of the mapping. If there is a mapping with the same sha256 hash then
         * a new {@link IndexMetadata} is returned with the found {@link MappingMetadata} instance, otherwise
         * the {@link MappingMetadata} instance of the indexMetadata parameter is recorded and the indexMetadata
         * parameter is then returned.
         */
        private IndexMetadata dedupeMapping(IndexMetadata indexMetadata) {
            if (indexMetadata.mapping() == null) {
                return indexMetadata;
            }
            String digest = indexMetadata.mapping().getSha256();
            MappingMetadata entry = mappingsByHash.get(digest);
            if (entry != null) {
                return indexMetadata.withMappingMetadata(entry);
            } else {
                mappingsByHash.put(digest, indexMetadata.mapping());
                return indexMetadata;
            }
        }
        /**
         * Similar to {@link #dedupeMapping(IndexMetadata)}.
         */
        private void dedupeMapping(IndexMetadata.Builder indexMetadataBuilder) {
            if (indexMetadataBuilder.mapping() == null) {
                return;
            }
            String digest = indexMetadataBuilder.mapping().getSha256();