[tap-mysql] discovery schema for json columns does not accept array types

[jamesmeneghello]

Current jsonschema output for a json field in MySQL is:

"type": [
  "null",
  "object"
]

However, this should also accept array, as MySQL JSON fields can store JSON arrays directly. Hence, any records containing JSON arrays currently fail schema validation during transfer.

[edgarrmondragon]

The standard workaround would be to use the Singer catalog to override the type, but the tap doesn't support it at the moment. See transferwise/pipelinewise-tap-mysql#186.