413 changehandle

[claireolmstead]

Problem

We do not have an endpoint to return an encoded payload for signing a change handle call.

Link to GitHub Issue(s): #413

Solution

• Create GET endpoint to return an encoded payload.
• Remove encoding from the POST change handle.

with @JoeCap08055 @enddynayn

Steps to Verify:

1. Get encoded extrinsic
2. Post change handle

[mattheworris]

• Read through changes
• Requesting updates to block expiration