JSON schema validation

Nobody has claimed this yet.

Ref: https://sqlfordevs.com/json-schema-validation

```sql

ALTER TABLE products ADD CONSTRAINT data_is_valid CHECK(
validate_json_schema(
'{
"type": "object",
"properties": {
"tags": {
"type": "array",
"items": { "type": "string" }
}
},
"additionalProperties": false
}',
attributes
)
);

INSERT INTO products (..., attributes) VALUES (..., '{}');
-- Result: OK
INSERT INTO products (..., attributes) VALUES (..., '{ "tags":[] }');
-- Result: OK
INSERT INTO products (..., attributes) VALUES (..., '{ "tags":["test"] }');
-- Result: OK
INSERT INTO products (..., attributes) VALUES (..., '{ "tags":[2] }');
-- ERROR: new row for relation "products" violates check constraint "data_is_valid"
-- DETAIL: Failing row contains ({"tags": [2]}).

```

No clue how we can use this magic, so I'm just jotting it down

Start by reading the linked sqlfordevs.com/json-schema-validation reference and the SQL example in this issue. Then determine what concrete Avram change is expected and how completion would be verified; the issue names no source files, tests, or specific behavior beyond recording the idea.

Written by the indexing model from the issue text.