Implemented the assignment of AssociatedXXXGroup for CSOM and SSOM

[andreasblueher]

Regarding my issue #1108 I've changed the corresponding handler, while the validators still remain empty.

[andreasblueher]

I've looked into the validators for prevalidating definitions and I was wondering if there's a way to check if more than 1 securitygroupdefinition has "AssociatedOwnerGroup = yes" assigned to it, because that could cause issues.

[SubPointSupport]

Yes, it is possible. We have an infrastructure to check three types of validity:

• a single definition itself
• a group of definition of the same type - multiple definitions
• relationships between definitions

All is under this namespace:

https://github.com/SubPointSolutions/spmeta2/tree/master/SPMeta2/SPMeta2/Validation/Validators

In this case, it would be a "collection" validator similar to FieldCollectionValidator

https://github.com/SubPointSolutions/spmeta2/blob/master/SPMeta2/SPMeta2/Validation/Validators/Collections/FieldCollectionValidator.cs

This API is rather old. There is another validation API under the following namespace:

https://github.com/SubPointSolutions/spmeta2/tree/master/SPMeta2/SPMeta2/Services/Impl/Validation

This one works similar to model handlers and has a broader access to the model tree.

[SubPointSupport]

Most likely this PR won't go. Waiting for @andreasblueher's review on the following work:

https://github.com/SubPointSolutions/spmeta2/issues/1108#issuecomment-390963801