Use builder pattern for Account transactions about starknet-rs

[xJonathanLEI]

Hmm I think one of the benefits of using this pattern is that we can hide away the complicated details (nonce & fees) from users. So I'd vote for not having to explicitly set use_next_nonce().

[xJonathanLEI]

What I have in mind is the following.

We should change the execute() method in Account trait to:

• not accept a nonce parameter; and
• return some new type AccountCall (as always, naming not final), which contains some send() method that will actually make the requests.

The proposed new type AccountCall will have these methods, apart from send():

• nonce()
• max_fee()

When send() is called, it'll use whatever nonce and max_fee supplied. If none is given, it will call get_nonce() and estimate_fees to figure out automatically.

@milancermak WDYT?

[milancermak]

Yes, this sounds great!

What do you think about having to use explicit and mutually exclusive setters for nonce / fee? So you'd either have to nonce(20) to set it as you wish or use_next_nonce() to get it from the get_nonce() call. I guess the only advantage is that the values are set explicitly instead of using a default. I have no strong feelings about this, just curious what your opinion is.