fix(databaseSources): be able to provide every types supported by flyway

[davinkevin]

The documentation provides an example for "flyway" usage with this jooq plugin.

When I try to use databaseSources with a value like listOf("filesystem:../database/migrations") this leads to this kind of error:

> Task :jooq-codegen-primary FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':jooq-codegen-primary'.
> Cannot convert URL 'filesystem:../database/migrations' to a file.

I need to use the filesystem:.. format of URL because my changelog is managed in another folder of my repository, outside of my kotlin project (because we generate an init-db container with this source files).

Do you think it could be possible to support this kind of file path?