Changelog for PR #4038: Port to apollo-compiler 1.0 beta (#4136)

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**Checklist**

Complete the checklist (and note appropriate exceptions) before the PR
is marked ready-for-review.

- [x] Changes are compatible[^1]
- [x] Documentation[^2] completed
- [x] Performance impact assessed and acceptable
- Tests added and passing[^3]
    - [ ] Unit Tests
    - [ ] Integration Tests
    - [ ] Manual Tests

**Exceptions**

*Note any exceptions here*

**Notes**

[^1]: It may be appropriate to bring upcoming changes to the attention
of other (impacted) groups. Please endeavour to do this before seeking
PR approval. The mechanism for doing this will vary considerably, so use
your judgement as to how and when to do this.
[^2]: Configuration is an important part of many changes. Where
applicable please try to document configuration examples.
[^3]: Tick whichever testing boxes are applicable. If you are adding
Manual Tests, please document the manual testing (extensively) in the
Exceptions.

.changesets/fix_simon_compiler_1_0.md

@@ -0,0 +1,13 @@
+### Port to apollo-compiler 1.0 beta ([PR #4038](https://github.com/apollographql/router/pull/4038))
+
+Version 1.0 is a near-complete rewrite of `apollo-compiler`.
+Using it in the Router unblocks a lot of upcoming work.
+
+As a more immediate benefit, some serialization-related bugs including 
+[Issue #3541](https://github.com/apollographql/router/issues/3541) are fixed.
+The representation of GraphQL documents in previous compiler versions was immutable.
+When modifying a query (such as to remove `@authenticated` fields from an unauthenticated request)
+the Router would build a new data structure with `apollo-encoder`, serialize it, and reparse it.
+`apollo-compiler`` 1.0 allows mutating a document in-place, skipping the serialization step entirely.
+
+By [@SimonSapin](https://github.com/SimonSapin) in https://github.com/apollographql/router/pull/4038