Poll model - validate end events (#3072)

* first cut poll model

* process incoming poll relations

* allow alt event types in relations model

* allow alt event types in relations model

* remove unneccesary checks on remove relation

* comment

* Revert "allow alt event types in relations model"

This reverts commit e578d84464.

* Revert "Revert "allow alt event types in relations model""

This reverts commit 515db7a8bc.

* basic handling for new poll relations

* tests

* test room.processPollEvents

* join processBeaconEvents and poll events in client

* tidy and set 23 copyrights

* use rooms instance of matrixClient

* tidy

* more copyright

* simplify processPollEvent code

* throw when poll start event has no roomId

* updates for events-sdk move

* more type changes for events-sdk changes

* validate poll end event senders

* reformatted copyright

* undo more comment reformatting

* fix poll end validation logic to allow poll creator to end poll regardless of redaction

* Update src/models/poll.ts

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

* correct creator == sender validationin poll end

---------

Co-authored-by: Richard van der Hoff <1389908+richvdh@users.noreply.github.com>

spec/test-utils/client.ts

@@ -60,6 +60,7 @@ export const getMockClientWithEventEmitter = (
  */
 export const mockClientMethodsUser = (userId = "@alice:domain") => ({
     getUserId: jest.fn().mockReturnValue(userId),
+    getSafeUserId: jest.fn().mockReturnValue(userId),
     getUser: jest.fn().mockReturnValue(new User(userId)),
     isGuest: jest.fn().mockReturnValue(false),
     mxcUrlToHttp: jest.fn().mockReturnValue("mock-mxcUrlToHttp"),