Access key provides limited access to an account. Each access key belongs to some account and
is identified by a unique (within the account) public key. One account may have large number of
access keys. Access keys allow to act on behalf of the account by restricting transactions
that can be issued.
account_id,public_key is a key in the state
Per account information stored in the state.
Grants limited permission to make transactions with FunctionCallActions
The permission can limit the allowed balance to be spent on the prepaid gas.
It also restrict the account ID of the receiver for this function call.
It also can restrict the method name for the allowed function calls.