Look up an id by a subject + schema pair:
curl -H "Content-type: text/plain" -XPOST "http://localhost:2876/schema-repo/tests/schema" -d '{"namespace":"tts.tests.avro","type":"record","name":"Test","fields":[{"name":"test_name","type":"string"},{"name":"ts","type":"int"},{"name":"value","type":["string","null"]}]}'