Djblets 3.3 gained standard types for standard JSON values, which is

great when deserializing. However, when preparing data to be serialized

to JSON, we often need to work with datetimes, lazy strings, UUIDs, and

objects that can be serialized to JSON.
To address this, we now have a new "serializable" set of JSON types,

which support all the values that DjbletsJSONEncoder (and parent

classes) support. This includes, date, time, datetime,

timedelta, UUID, Promise, and Decimal values, along with

functions containing a to_json() method.
DjbletsJSONEncoder has been updated to include the typing support as

well, primarily for consistency and to help test the types. It also

drops explicit support for Promise (lazy strings), since Django's

encoder supports that internally these days.
Also of note, this does not contain typing used by the WebAPI resource

support. These types only work with this encoder and not the resource

encoder.

Unit tests pass in Djblets and Review Board.
Made use of these new types in some in-progress code.