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 this;
        }
        /**
         * Adds a map of namespace to {@link ReservedStateMetadata} into the metadata builder
         * @param reservedStateMetadata a map of namespace to {@link ReservedStateMetadata}
         * @return {@link Builder}
         */
        public Builder put(Map<String, ReservedStateMetadata> reservedStateMetadata) {
            this.reservedStateMetadata.putAll(reservedStateMetadata);
            return this;
        }
        /**
         * Adds a {@link ReservedStateMetadata} for a given namespace to the metadata builder
         * @param metadata a {@link ReservedStateMetadata}
         * @return {@link Builder}
         */
        public Builder put(ReservedStateMetadata metadata) {
            reservedStateMetadata.put(metadata.namespace(), metadata);
            return this;
        }
        /**
         * Removes a {@link ReservedStateMetadata} for a given namespace
         * @param metadata a {@link ReservedStateMetadata}
         * @return {@link Builder}
         */
        public Builder removeReservedState(ReservedStateMetadata metadata) {
            reservedStateMetadata.remove(metadata.namespace());
            return this;
        }
        public Builder indexGraveyard(final IndexGraveyard indexGraveyard) {