Previously invalid REST endpoints would throw errors during schema cache build.
This PR changes the validation to instead add to the inconsistent metadata objects in order to allow use of `allow_inconsistent_metadata` with inconsistent REST endpoints.
All non-fatal endpoint definition errors are returned as inconsistent metadata warnings/errors depending on the use of `allow_inconsistent_metadata`. The endpoints with issues are then created and return informational runtime errors when they are called.
Console impact when creating endpoints is that error messages now refer to metadata inconsistencies rather than REST feature at the top level:
<img width="969" alt="image" src="https://user-images.githubusercontent.com/92299/110258597-8336fa00-7ff7-11eb-872c-bfca945aa0e8.png">
Note: Conflicting endpoints generate one error per conflicting set of endpoints due to the implementation of `groupInconsistentMetadataById` and `imObjectIds`. This is done to ensure that error messages are terse, but may pose errors if there are some assumptions made surrounding `imObjectIds`.
Related to https://github.com/hasura/graphql-engine-mono/pull/473 (Allow Inconsistent Metadata (v2) #473 (Merged))
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### Kodiak commit message
Changes the validation to use inconsistent metadata objects for REST endpoint issues.
#### Commit title
Inconsistent metadata for REST endpoints
GitOrigin-RevId: b9de971208e9bb0a319c57df8dace44cb115ff66
Resolves Issues:
* https://github.com/hasura/graphql-engine-mono/issues/658 - Invalid Slashes
* https://github.com/hasura/graphql-engine-mono/issues/628 - Subscriptions
Implementation:
* Moved some logic from Endpoint.hs to allow reuse of splitting url into PathSegments.
* Additional validation steps alongside checking for overlapping routes
* Logging potential misuse of GET for mutations
Future Work:
* [ ] GET is allowed for mutations (Ignore/Log warning for Now)
* [ ] Add to scInconsistentObjs rather than throwing error
* Add information to scInconsistentObjs instead of raising errors directly.
TODO:
* [x] Duplicate variable segments with the same name in the location should not be allowed
* [x] We should throw an error on trailing and leading slashes and URLs which contain empty segments
* [x] Endpoints can be created using subscriptions. But the error only shows at the time of the query
* [x] Tests
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### Kodiak commit message
Prohibit Invalid slashes, duplicate variables, subscriptions for REST endpoints.
GitOrigin-RevId: 86c0d4af97984c8afd02699e6071e9c1658710b8
