We allow inserting column values using a JSON value, eg:
```cql
INSERT INTO mytable JSON '{ "\"myKey\"": 0, "value": 0}';
```
When no JSON value is specified, the query should be rejected.
Scylla used to crash in such cases. A recent change fixed the crash
(https://github.com/scylladb/scylladb/pull/14706), it now fails
on unwrapping an uninitialized value, but really it should
be rejected at the parsing stage, so let's fix the grammar so that
it doesn't allow JSON queries without JSON values.
A unit test is added to prevent regressions.
Refs: https://github.com/scylladb/scylladb/pull/14707
Fixes: https://github.com/scylladb/scylladb/issues/14709
Signed-off-by: Jan Ciolek <jan.ciolek@scylladb.com>
\Closes #14785
(cherry picked from commit cbc97b41d4)
cd9458eeb1