ITransformEntriesToTypeConfig.identityKey does not return Promise in type definitions

[gigaSproule]

Expected Behavior

ITransformEntriesToTypeConfig should have the type definition for identityKey return a Promise as per https://github.com/contentful/contentful-migration/blob/master/src/lib/action/entry-transform-to-type.ts#L13.

Actual Behavior

Get the typescript error "Type '(fields: ContentFields) => Promise<string | undefined>' is not assignable to type '(fromFields: ContentFields) => string'.
Type 'Promise<string | undefined>' is not assignable to type 'string'.ts(2322)".

Possible Solution

Add Promise to type information for function.

Steps to Reproduce

1. Create a migration script which calls transformEntriesToType
2. Pass in a function for identityKey which returns a Promise
3. Try to compile with tsc

Context

Environment

• Node Version: v14.19.3
• Package Manager Version: yarn 1.18.0
• Operating System: Arch Linux
• Package Version: 4.8.1