WIP: DT-982: New Support APIs

[rushtong]

WIP

Addresses

Partially https://broadworkbench.atlassian.net/browse/DT-982

Summary

• Provide new API to post a support request to DSP's Zendesk instance.
• This does NOT provide a mechanism for uploading attachments. That will be addressed in a future PR in order to keep this PR manageable. However, if attachments have been previously uploaded, this code will accept an attachmentToken which refers to previously uploaded attachments.

Notes for reviewers

• There was existing service code to handleInstitutionSOSupportRequest which is no longer a feature, so it is removed in this PR.

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