setRules endpoint for Storage Emulator

[samtstern]

Description

Needed to implement some version of:
firebase/firebase-js-sdk#4863

Scenarios Tested

Good Rules

Bad Rules

Bad Requests

Sample Commands

N/A

[abeisgoat]

Do the other emulators also return a non-json response? I feel like making that machine readable would be ideal

[samtstern]

Do the other emulators also return a non-json response? I feel like making that machine readable would be ideal

I can change this to a simple JSON object like { "message": ... } but I hesitate to include the whole issues payload since right now there is no code which will actually consume it and therefore it's just making an API promise earlier than we need to.