Integrations tests

[shogunpurple]

Description

This PR contains unit tests for all the current external data source integrations. Due to the integration heavy nature - the actual database/datasource layers are heavily mocked with Jest. These tests cover the functionality within the integration classes themselves, making sure that the right values are passed through to the respective database clients.

Also included some bug fixes and consistency issues here - so that clients can expect a consistent API when interacting with SQL databases.

Screenshots

Coverage after integrations tests:

[mike12345567]

LGTM! This is excellent! we'll be green across the board once the relationship tests are in too!

One thing I would say is that in the package.json in the jest.collectCoverageFrom you can exclude the test directory from coverage which stops it from showing up anyway in the coverage report. Can do "!src/integrations/tests/**/*" to exclude everything, whether its a spec file or a JS file of some sort (like a utility).

Love the use of the __mocks__ directory for these integrations, means if we want to build up any behavioural tests or something like that in the future for any specific database quite easy to setup mocked values and so on.