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
}
    @Override
    public Diff<Metadata> diff(Metadata previousState) {
        return new MetadataDiff(previousState, this);
    }
    public static Diff<Metadata> readDiffFrom(StreamInput in) throws IOException {
        if (in.getTransportVersion().onOrAfter(MetadataDiff.NOOP_METADATA_DIFF_VERSION) && in.readBoolean()) {
            return SimpleDiffable.empty();
        }
        return new MetadataDiff(in);
    }
    public static Metadata fromXContent(XContentParser parser) throws IOException {
        return Builder.fromXContent(parser);
    }
    @Override
    public Iterator<? extends ToXContent> toXContentChunked(ToXContent.Params p) {
        XContentContext context = XContentContext.valueOf(p.param(CONTEXT_MODE_PARAM, CONTEXT_MODE_API));
        final Iterator<? extends ToXContent> start = context == XContentContext.API
            ? ChunkedToXContentHelper.startObject("metadata")
            : Iterators.single((builder, params) -> builder.startObject("meta-data").field("version", version()));
        final Iterator<? extends ToXContent> persistentSettings = context != XContentContext.API && persistentSettings().isEmpty() == false
            ? Iterators.single((builder, params) -> {
                builder.startObject("settings");
                persistentSettings().toXContent(builder, new ToXContent.MapParams(Collections.singletonMap("flat_settings", "true")));
                return builder.endObject();
            })
            : Collections.emptyIterator();
        final Iterator<? extends ToXContent> indices = context == XContentContext.API
            ? ChunkedToXContentHelper.wrapWithObject("indices", indices().values().iterator())
            : Collections.emptyIterator();