Add endpoint exposing data write (or all) fee details

[cptartur]

What problem does your feature solve?

Currently, it's not easily possible (or not possible at all) to get the fees breakdown for writing data to the ledger.

What would you like to see?

Add a new endpoint which exposes the current fee details. I propose that for future proofing it exposes all fees, even the ones that do not change dynamically i.e. all fees included in this documentation page:

https://developers.stellar.org/docs/reference/resource-limits-fees#resource-fees

Additionally, values like minimum TTL for entries could be provided in the endpoint output as well.

What alternatives are there?

A minimal viable solution would just be an endpoint that provides the fee of writing to the ledger, without the data on other fees.

[cptartur]

What we could consider is also providing the details on fees paid for the sent transaction. This would be a nice to have feature for reference. However, only implementing this without creating a separate endpoint for fees would not resolve the issue.

[mollykarcher]

@cptartur thanks for reporting! I'm going to close this as a duplicate of #114, but please comment over there and/or reopen if you think that solution won't suit your needs.