Allow ability to group Type Mappings

[DnOberon]

Reason

We need the ability to group mappings together and edit transformations, or apply them for all mappings at once in the UI - and then have that respected by the processing thread. This is important because it will allow us to more swiftly build type mappings.

Design

• Allow groupings by creating a join table - a many to many relationships where one mapping is the "parent" and each child mapping is attached to it via a join record.
• UI modified to reflect this ability and change
• When transformations are saved on a mapping group, it is only saved to the "parent" mapping this also allows for a mapping to belong to multiple groups)
• When mappings are removed from the group, all transformations for the group are copied to them on removal
• Transformation UI updated to reflect all possible keys from the multiple payloads due to multiple mappings
• Processing thread updated to fetch all groups a mapping is a part of, then fetch all transformations from those groups
• Export/Import of mappings updated to also accept and export a list of groupings (MUST BE FULLY BACKWARDS COMPATIBLE)

Impact

Impacts the processing thread, but everything MUST BE FULLY BACKWARDS COMPATIBLE