feat(api): API specification v2.18.0

* feat(edu): Released Resource Library API in beta (`/eduResources`) with new OAuth 2 scopes `edu.resources` and `edu.resources.readonly`.
* feat(edu): Updated `POST /classes/{class}/assignments/{assignment}/copy` to allow to copy to Resource Library.
* feat(edu): Updated `DELETE /classes/{class}/assignments/{assignment}/submissions/{submission}` behavior, now only resets the submission instead of deleting it.
* feat(edu): Added `POST /classes/{class}/testStudent` to create testing student accounts.
* feat(edu): Operation `POST /classes/{class}/assignments` has been renamed from `createAssignment` -> `createClassAssignment` in schema.
* feat(edu): `Assignment` models now include a new `capabilities` property returning which actions are possible with a specific resource (`canEdit`, `canPublishInClass`, `canPublishInClassError`, `canArchive`, `canUnarchive`).
* feat(edu): `Assignment` models now include a new `useDedicatedAttachments` property to know if the underlying resources are dedicated and stored inside the assignment (new behavior with the resource library).
* feat(edu): `ClassAssignment` now includes a new `issue` property to return any issues encountered with the assignment.
* feat(edu): `toolset` id provided when creating or updated assignments will now make a copy of the toolset to have a dedicated object for the assignment.
* feat(edu): `AssignmentSubmissionHistory` now includes the `source` of the change, when this one comes from a third party (Google Classroom, Microsoft Teams, LTI). It also includes the following new properties: `dueDate`, `comment` and `attachment.title`.
* feat(edu): `UserDetails` now contains Microsoft Sign in details (`azureDetails`) and list of groups the user is part of (`groups`).
* feat(edu): Added optional metadata on class objects (`level`, `skillsFocused`, `size`).
* fix(edu): Fixed `ClassAttachmentCreation` enum values to reflect the current state of our product.
* feat(scores): Updated `GET /scores/{score}/revisions/{revision}` now returns the `startDate` and `endDate` for the score revisions.
* feat(scores): Updated `POST /scores` to add `hasQuarterTone` on score builders to enable quarter tones on score parts.
* feat(scores): Updated `POST /scores/{score}/fork` to add option to keep original title during a file copy (`keepOriginalTitle`).
* fix(schema): Added missing required properties on models `ScoreSummary`, `MediaAttachment` and `FlatErrorResponse`.