use user managed identity to auth to speech instead of key

[yungezz]

Purpose

• use user MI to auth to speech instead of key.
• since app code isn't completely ready, this is a draft PR as a sample on how to use user managed identity.
• Another part of change to make user MI work is to update /infra module biceps, such as creating a user managed identity, grant speech RBAC role to it etc. Since /infra folder isn't ready now, the change will be made after that.

Does this introduce a breaking change?

[ ] Yes
[ ] No

Pull Request Type

What kind of change does this Pull Request introduce?

[ ] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:

How to Test

• Get the code

git clone [repo-address]
cd [repo-name]
git checkout [branch-name]
npm install

• Test the code

What to Check

Verify that the following are valid

• ...

Other Information

[marlenezw]

Thanks for this PR @yungezz! I'll start testing locally and make changes directly to this PR and merge once changes are good. I've marked the PR ready for review but let me know if you'd prefer that I make a seperate PR? Thanks

[marlenezw]

Actually, there are a bunch of updates that have been made in main that would need to be changed to merge this in. Let me create a sepearte PR for the moment