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/test/java/org/elasticsearch/cluster/metadata/MetadataTests.java
final BytesStreamOutput out = new BytesStreamOutput();
        originalMeta.writeTo(out);
        NamedWriteableRegistry namedWriteableRegistry = new NamedWriteableRegistry(ClusterModule.getNamedWriteables());
        final Metadata fromStreamMeta = Metadata.readFrom(
            new NamedWriteableAwareStreamInput(out.bytes().streamInput(), namedWriteableRegistry)
        );
        assertThat(fromStreamMeta.clusterUUID(), equalTo(originalMeta.clusterUUID()));
        assertThat(fromStreamMeta.clusterUUIDCommitted(), equalTo(originalMeta.clusterUUIDCommitted()));
    }
    public void testMetadataGlobalStateChangesOnClusterUUIDChanges() {
        final Metadata metadata1 = Metadata.builder().clusterUUID(UUIDs.randomBase64UUID()).clusterUUIDCommitted(randomBoolean()).build();
        final Metadata metadata2 = Metadata.builder(metadata1).clusterUUID(UUIDs.randomBase64UUID()).build();
        final Metadata metadata3 = Metadata.builder(metadata1).clusterUUIDCommitted(metadata1.clusterUUIDCommitted() == false).build();
        assertFalse(Metadata.isGlobalStateEquals(metadata1, metadata2));
        assertFalse(Metadata.isGlobalStateEquals(metadata1, metadata3));
        final Metadata metadata4 = Metadata.builder(metadata2).clusterUUID(metadata1.clusterUUID()).build();
        assertTrue(Metadata.isGlobalStateEquals(metadata1, metadata4));
    }
    private static CoordinationMetadata.VotingConfiguration randomVotingConfig() {
        return new CoordinationMetadata.VotingConfiguration(Sets.newHashSet(generateRandomStringArray(randomInt(10), 20, false)));
    }
    private Set<VotingConfigExclusion> randomVotingConfigExclusions() {
        final int size = randomIntBetween(0, 10);
        final Set<VotingConfigExclusion> nodes = Sets.newHashSetWithExpectedSize(size);
        while (nodes.size() < size) {
            assertTrue(nodes.add(new VotingConfigExclusion(randomAlphaOfLength(10), randomAlphaOfLength(10))));
        }
        return nodes;
    }
    public void testXContentWithCoordinationMetadata() throws IOException {