Add API endpoint to fetch information about a legacy wallet.

[jonathanknowles]

Context

This task will provide an API endpoint that allows users to fetch information about a Byron wallet.

In order to use this endpoint for a given wallet, the wallet must have been previously restored with the postByronWallet endpoint.

Decision

The API will provide an endpoint similar to the following:

/byron/wallets/{byronWalletId}:
  get:  
    operationId: getByronWallet  
    tags: ["Wallets"]
    summary: Get
    description: Return information about a Byron wallet. 
    parameters:
      - *parametersByronWalletId 
    responses: *responsesGetByronWallet

With schema definitions similar to the following:

x-responsesGetByronWallet: &responsesGetByronWallet 
  <<: *responsesErr404
  <<: *responsesErr405
  <<: *responsesErr406
  200:
    description: Ok   
    schema: *ApiByronWallet  

See ApiByronWallet definition.

Acceptance Criteria

Within the list of criteria below, a ticked criterion indicates that there is test coverage in the master branch to demonstrate that this criterion is satisfied.

• The API must provide an endpoint to fetch information about a legacy wallet.
• After a successful restore with restoreByronWallet, calling getByronWallet must return a valid ApiByronWallet object with information about the restored wallet.
• After a successful deletion with deleteByronWallet, calling getByronWallet must return an error.

Development Plan

• Implement dummy endpoint that always fails with a suitable wallet not found error.
  This will unblock tasks that depend on the presence of this endpoint and types relating to it.
• Replace dummy implementation with real implementation.

PR

Number	Base
#790	master
#817	master
#846	master

QA

• Build integration tests to verify that all acceptance criteria have been satisfied.

[piotr-iohk]

lgtm!