docs: create 'concepts' page on scopes

[ahal]

Rendered

[ahal]

@matt-boris @petemoore @lotas hey TC team, I wrote up this doc because I realized that even I was feeling fuzzy on how scopes actually work under the hood. Could one of you do a quick proof read of the Queue and Auth Services section just to make sure I have it more or less right?

[bhearsum]

This looks like a very nice overview, thanks for writing it!

Two things you could consider also adding here:

• A brief bit on how scopes and decision tasks relate. Eg: that a decision task itself must have all of the scopes for all of the tasks that will create, and then the individual tasks are only granted the specific things they need. (I found this surprising and a bit confusing when I learned about it.)
• A brief explanation of roles

If you think either of these are out of scope or too in the weeds that's totally fine.

[ahal]

Thanks for the suggestions, I incorporated them in!