Create API to provide subkeys for a given key

[JonRay15]

API Overview

As part of the AMM implementation, keys can now have a subkey from which the AMM commitment is handled.

As a result we need a way to link from the parent key to its subkeys.

I have included on #11023 the potential option to just include the parent key on the AMM shape, which might be a simple way to handle this since I think right now subkey and parent key are always 1-2-1?

But maybe it is better to have an API for this in case we have more subkeys of more types later? So including this so it can be considered.

API request details

• Create an API listing parent keys and providing for each parent key
  • Any subkeys
  • The type of subkey (vAMM, other)

Filtering requirements (inputs)

• Parent key
• Subkey
• Type

Questions

TBC

API test scenarios

Detailed scenarios that can be executed as feature tests to verify that the API has been implemented as expected.

GIVEN (setup/context)
WHEN (action)
THEN (assertion) For example...
See here for more format information and examples.

Additional Details (optional)

Any additional information that provides context or gives information that will help us develop the feature.

[JonRay15]

Now covered elsewhere