Get all series metadata matching the given filter.
application/json
{"filter": ["and", ["key", "system"], ["=", "role", "database"]]}
$ curl -XPOST -H "Content-Type: application/json"
http://localhost:8080/metadata/series \
-d '{"filter": ["and", ["key", "system"], ["=", "role", "database"]]}'
[
{"key": "foo", "tags": {"site": "lon"}},
{"key": "foo", "tags": {"site": "sto"}}
]