Encoding and user_id bug fixes LRN-43802 LRN-44754 LRN-44748

[david-scarratt-lrn]

Checklist

• [ ] Feature

• [x] Bug

• [x] ChangeLog.md updated

• [x] Tests added

• [x] All testsuite passes

• [ ] make dist completed successfully

[sreenivasa-murty-lrn]

User Story :- https://learnosity.atlassian.net/browse/LRN-44748 CheeryPicked the commit hashes into https://github.com/Learnosity/learnosity-sdk-php/pull/85. Hence closing this PR.