Plone.restapi

New features:

- Improve extensibility story for resolveUID field
serializer/deserializer sneridagh (1179)

Bug fixes:

- Wrong deserialization if the path does not exist but is matched via
acquisition sneridagh (1176)

New features:

- Set UID of a content during creation if the user has Manage Portal
permission. ericof (497)

New features:

- Remove Python 2, Plone 4.3, and 5.1 code. ericof (1140)

Bug fixes:

- In src run `find . -name "*.py"|xargs pyupgrade
--py36-plus`. Then run black and remove six import
leftovers. jensens (1162)
- Fix link content serialization when url points to local content but
it does not exist sneridagh (1167)
- Fix navigation service not using nav_title metadata. ericof
(1169)

Bug fixes:

- Fix interpolation variable present in response after serialization
sneridagh (1164)