Support injecting providers into dataSourceFactory

[brandon-leapyear]

Is there an existing issue that is already proposing this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe it

I would like to provide my own DataSource, but I need to inject my ConfigService so that I can do things in my DataSource depending on configuration.

Describe the solution you'd like

The most straightforward solution is to provide a dataSourceFactoryInject option.

A bigger change (which I think makes more sense) would be to remove dataSourceFactory and add

dataSourceProviderModify: (provider) => provider
entityManagerProviderModify: (provider) => provider

which passes in the default provider, and the user can modify whatever they want, e.g.

dataSourceProviderModify: (provider) => ({
  ...provider,
  useFactory: (typeOrmOptions, configService) => {
    return new MyDataSource(typeOrmOptions, configService)
  },
  inject: [...provider.inject, ConfigService],
})

Teachability, documentation, adoption, migration strategy

See solution.

What is the motivation / use case for changing the behavior?

See problem.

[khanh-le-otsv]

I would like to suggest this feature as well.