Add filter extension (#825)

* feat: add filter extension to conformance

* feat: add cql2 filter extension for POST

* fix: remove commented code, get rid of .only in tes

* feat: cql2 filter extension for GET

* fix: use fully qualified property names

* test: remove redundant test

- decided to not handle filter={}; let it fail

* build: 'npm audit fix' to get CI passing

* feat: check for correct filter-lang and filter-crs

* feat: Add filter extension to aggregate endpoint

* docs: update CHANGELOG

* test: add test for top level field and property in filter extension filter

* review: move constants out of function

* review: stacQlQuery -> stacqlQuery

* review: buildQuery -> buildOpenSearchQuery

* review: Add minimum_should_match = 1 for 'should' clauses

* fix: remove .only from test, update a test comment

* review: remove explicit prefixing of properties object fields

* feat: raise error when collection queryables has additionalProperties set to false

* style: align existing test format

* feat: add query and filter extensions to openapi.yaml

* docs: update README.md

* fix: finish adding filters extension to the OpenAPI spec

* fix: minor changes to query extension in openapi.yaml

* docs: augument CHANGELOG entry, tweak extension list in README

* review: remove bbox from UNPREFIXED_FIELDS

* review: clarify that fields **must not** be prefixed

* review: add deprecated note to Context Extension

* review: Add note about filter expression terms exactly matching Item properties fields

* review: add back bbox and note that bbox and geometry are not yet supported for filtering

* review: add back bbox

CHANGELOG.md

@@ -5,6 +5,14 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Added
+
+- Minimum implementation (basic-cql2 conformance class) of the filter extension for the
+  `/search` (GET and POST), `/collections/{collectionId}/items` (GET), and `/aggregate`
+  (GET) endpoints. Only CQL2 JSON is supported.
+
 ## [3.8.0] - 2024-05-29
 
 ### Changed
@@ -465,6 +473,7 @@ Initial release, forked from [sat-api](https://github.com/sat-utils/sat-api/tree
 Compliant with STAC 0.9.0
 
 <!-- [unreleased]: https://github.com/stac-utils/stac-api/compare/v3.6.0...main -->
+
 [3.7.0]: https://github.com/stac-utils/stac-api/compare/v3.6.0...v3.7.0
 [3.6.0]: https://github.com/stac-utils/stac-api/compare/v3.5.0...v3.6.0
 [3.5.0]: https://github.com/stac-utils/stac-api/compare/v3.4.0...v3.5.0