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
assertThat(metadata.getMappingsByHash(), aMapWithSize(randomMappingDefinitions.size() + 1));
        assertThat(metadata.getMappingsByHash().get(newMapping.getSha256()), equalTo(newMapping));
        {
            Metadata.Builder mb = new Metadata.Builder(metadata);
            mb.remove("index-" + numIndices);
            metadata = mb.build();
        }
        assertThat(metadata.getMappingsByHash(), aMapWithSize(randomMappingDefinitions.size()));
        assertThat(metadata.getMappingsByHash().get(newMapping.getSha256()), nullValue());
    }
    public void testWithLifecycleState() {
        String indexName = "my-index";
        String indexUUID = randomAlphaOfLength(10);
        Metadata metadata1 = Metadata.builder(randomMetadata())
            .put(
                IndexMetadata.builder(indexName)
                    .settings(settings(IndexVersion.current()).put(IndexMetadata.SETTING_INDEX_UUID, indexUUID))
                    .creationDate(randomNonNegativeLong())
                    .numberOfShards(1)
                    .numberOfReplicas(0)
            )
            .build();
        IndexMetadata index1 = metadata1.index(indexName);
        assertThat(metadata1.getIndicesLookup(), notNullValue());
        assertThat(index1.getLifecycleExecutionState(), sameInstance(LifecycleExecutionState.EMPTY_STATE));
        LifecycleExecutionState state = LifecycleExecutionState.builder().setPhase("phase").setAction("action").setStep("step").build();
        Metadata metadata2 = metadata1.withLifecycleState(index1.getIndex(), state);
        IndexMetadata index2 = metadata2.index(indexName);
        
        assertThat(metadata2.getIndicesLookup(), sameInstance(metadata1.getIndicesLookup()));