Included custom data field sets are now nullable

[vestrel00]

Problem

Due to changes in #321, the following custom data components now take in nullable custom data field sets (e.g. Set<AbstractCustomDataField>?).

When upgrading to the latest release, library users that define their own custom data will run into compiler errors in implementations of;

• AbstractCustomDataCursor
• AbstractCustomDataEntityMapper.Factory
• AbstractCustomDataOperation
• AbstractCustomDataOperation.Factory

Solution

Notify library users of this breaking change!

• Close this issue along with Add option to disable included field validation checks in all insert, update, and query APIs #321
• Provide migration guide.

[vestrel00]

Migration guide (to be included in release notes)

Fix compile errors by making Set<AbstractCustomDataField> nullable -> Set<AbstractCustomDataField>?

For example, change this...

internal class HandleNameMapperFactory {
    override fun create(
        ... includeFields: Set<HandleNameField>
    ) = HandleNameMapper(HandleNameDataCursor(cursor, includeFields))
}

to this...

internal class HandleNameMapperFactory {
    override fun create(
        ... includeFields: Set<HandleNameField>?
    ) = HandleNameMapper(HandleNameDataCursor(cursor, includeFields))
}

[vestrel00]

This is included in release 0.3.2.