[BitSail][Optimization] Improve FakeSource connector.

[BlockLiu]

Describe the problem or proposal

Improve FakeSource connectors.

Task List

• [ ] #242
• [ ] #244

Are you willing to submit PR?

• [ ] Yes I am willing to submit a PR.

[kyle-hawk]

Fake Connector does not seem to be able to declare whether the field is nullable, this can be useful sometimes @BlockLiu

[kyle-hawk]

Fake Connector support bigdecimal field, but seems not support specifying precision and scale, like this

        {
          "name": "decimal_type",
          "type": "bigdecimal(9,9)"
        }

this can be useful when we test decimal fields of sink connectors

[BlockLiu]

Yep, Fake connector is quite simple and can only be used for functional tests. It's weak for data verification tests. Would you like to improve it?

[kyle-hawk]

sure, I'd like to join to improve this