[Holders] Get balance list and balance for an account

[dhythm]

Is your feature request related to a problem? Please describe.

Holders api needs token_address at the moment.
So it needs to get all tokens (n) and get all holders (m) (= n * m requests) if we want to get balance for an account.

Describe the solution you'd like

To get balances of holding tokens for an account (an EOA).

Describe alternatives you've considered

To call API with EOA of an account, then return all balances of holding tokens

Additional context

nothing.

[urushibata-k]

URL: GET: /position/{account_address}
Header param:

• issuer-address: optional

Query param:

• token_type: optional
• offset: optional
• limit: optional

---

URL: GET: /position/{account_address}/{token_address}
Header param:

• issuer-address: required

[dhythm]

I would be awesome if the return value includes token_name, token_address and balance 🙏