admin/server: fix get_cluster_id response formatting

[andijcr]

Unwrap the cluster_uuid_t type when formatting the response

Fixes #16162

Backports Required

• none - not a bug fix
• none - this is a backport
• none - issue does not exist in previous branches
• none - papercut/not impactful enough to backport
• v23.3.x
• v23.2.x
• v23.1.x

Release Notes

Improvements

• get_cluster_uuid returns a correctly formatted string

[vbotbuildovich]

new failures in https://buildkite.com/redpanda/redpanda/builds/43975#018d2311-24e7-4719-b859-5b1d9cd4b288:

"rptest.tests.topic_creation_test.TopicRecreateTest.test_topic_recreation_while_producing.workload=IDEMPOTENT.cleanup_policy=compact"

[andijcr]

issue is #16036 in dev

[dotnwat]

we should have a test that checks the output format since this is an external facing interface?

[andijcr]

we should have a test that checks the output format since this is an external facing interface?

interestingly in cluster_manifest.json we correctly unwrap uuid. here

redpanda/tests/rptest/tests/cluster_metadata_upload_test.py

Lines 156 to 165 in 0afd0bd

	orig_cluster_uuid_resp: str = admin.get_cluster_uuid(
	self.redpanda.nodes[0])
	# Wipe the directory away, simulating a full cluster outage.
	self.redpanda.stop()
	s3_snapshot = BucketView(self.redpanda, topics=self.topics)
	orig_cluster_uuid, orig_highest_manifest_id = \
	check_cluster_metadata_is_consistent(s3_snapshot)
	assert orig_cluster_uuid in orig_cluster_uuid_resp, \
	f"{orig_cluster_uuid_resp} vs {orig_cluster_uuid}"

we compare the uuid from a cluster_manifest.json against the response from admin API by doing
orig_cluster_uuid in orig_cluster_uuid_resp instead of orig_cluster_uuid == orig_cluster_uuid_resp so that test was coded to be resilient. i'm adding a ducktape test

[michael-redpanda]

lgtm

[andijcr]

/backport v23.3.x

[vbotbuildovich]

/backport v23.3.x