Pass through all possible stitching errors

[yaacovCR]

This PR aims to solve the same issues as #1074 (i.e., #743, #1037, #1046, apollographql/apollo-server#1582).

It does so by:

• making sure to not use object spread notation with GraphQL error objects, as these are not plain objects.
• using a new relocatedError function based on locatedError to change a GraphQL error path.
• remove distinction between OWN and CHILDREN errors within error annotation; when null, both must be thrown, as otherwise children errors will never be thrown.

TODO (finished)

• If this PR is a new feature, reference an issue where a consensus about the design was reached (not necessary for small changes)
• Make sure all of the significant new logic is covered by tests
• Rebase your changes on master so that they can be merged easily
• Make sure all tests and linter rules pass
• Update CHANGELOG.md with your change. Include a description of your change, link to PR (always) and issue (if applicable). Add your CHANGELOG entry under vNEXT. Do not create a new version number for your change yourself.

[yaacovCR]

Just to comment on graphql-tools-fork, where this pull request will likely actually be merged soon.

In general, the aim of the fork is to (A) actually get fixes merged and (B) stop the deprecations of useful functionality. In particular, I think schema stitching/delegation should not be deprecated -- it seems still very useful, especially with delegation to external GraphQL APIs.

One stated rationale for deprecation was that schema stitching is brittle; I think merging bug fixes will show that it is less brittle than thought. :)

I also believe that there may exist simpler solutions to the problems that schema federation is meant to solve, and that the schema delegation/stitching API gives the community the low-level tools to continue to experiment. More on this when time allows and in separate issues.

[yaacovCR]

Comments, feedback, opposing viewpoints welcome!

[yaacovCR]

Released to graphql-tools-fork as v5.1.0.

[yaacovCR]

Similar to #1104 and #1131, failing tests are external to this change and fixed by #1102.

[despairblue]

@yaacovCR I'm hitting the same error. Was this PR superseded by something else or did you close it because you received no response?

[despairblue]

Nevemind, found #1206 👍