Feature request: `formerlyKnownAs(oldName)`

[ViliamKopecky]

When renaming fields and entities there are (at least) 2 problems:

• Need to manually modify migration file.
• Back compatibilty.

I got an idea to have formerlyKnownAs decorators for both entites and fields.

@def.formerlyKnownAs('Folder')
export class Directory {
    name = def.stringColumn().formerlyKnownAs('title')
}

• Contember would know that it should generate migration using rename strategy.
• GraphQL schema could keep providing data under old name for back compatibility, until developer removes formerlyKnownAs.

Bonus: something similar could even handle mapping enum values. It could map values during migration, and keep accepting old values and storing them as mapped new values.

const OldType = def.createEnum('a', 'b', 'c')
const Type = def.createEnum('c', 'd', 'e')

export class Directory {
    type = def.enumColumn(Type).deprecate(OldType, { a: null, b: 'c' })
}