Document updates produce incorrect DAG state.

[jsimnz]

Describe the problem
DAG nodes from update mutations contain more than just the fields changed, they contain all the fields defined along with the field(s) changed.

To Reproduce
Create a document, update a document, run a commit request for the composite type. Will show a commit with all fields included in the update, when it

Expected behavior
should only include the newest field(s) (delta)

Additional context
Potentially related to the LensFetcher, havent confirmed, works in 0.5.1, broken in 0.6.0

[AndrewSisley]

This might only affect updates via the planner/gql, as collection.Save (via an UpdateDoc test action) appears to be covered by the semi-broken looking TestQueryCommitsWithDockeyAndUpdateAndLinks. We should definitely have more tests than just this one, for both requests and collection sourced updates.

We actually have a fair few tests for this (e.g. TestQueryCommitsWithFieldNameFieldAndUpdate), it very much appears to be working via collection.Save.

We do however have no tests for gql/request updates - this does appear to be broken, and this test gap needs to be closed.

[AndrewSisley]

Will likely fix the bug as part of #1816

[AndrewSisley]

Lens fetcher does not appear to be responsible. Leading candidate is the fetcher interface simplication.