Improve builders by reworking usage of context managers and adding ability to remove elements.
Features:
- Verification methods, references, and services can now be added to builders in the following manner:
python
builder.verification_methods.add(...)
builder.authentication.embed(...)
builder.authentication.reference(...)
builder.service.add(...)
- Verification methods, references, and services can now be removed from builders (completing the CRUD operations of DID Documents as delegated to the DIDDocumentBuilder)
Breaking Changes:
- `builder.verification_methods(default_suite=...)` is now `builder.verification_methods.defaults(suite=...)`
- Removed `DIDDocument.to_builder()`. Use `DIDDocumentBuilder.from_doc(doc)` instead.