Apply pagination macro to all requests

[kevin-pease]

✨ What kind of change does this PR introduce? (Bug fix, feature, docs update...)

Fixes #59.

• Applies the pagination macro in all endpoints (except accounts, see below), and removes duplicate code. Some tests needed to be updated slightly (for example, unwrap needed to be appended in some locations.

• Adds a check in the pagination macro itself (set_cursor), which was previously present in some pagination implementations. This way, one uniform error message will always be returned.

• Updates relevant documentation examples with the addition of required crate imports for the macro.

Note: Accounts endpoint still needs to be refactored, but the pagination macro needs to be updated first, due to generics. See #70.

⤵️ What is the current behavior?

Similar implementations of pagination functionality are present in some endpoints, which results in duplicate code. Also, there are minor differences between these implementation, leading to inconsistencies.

🆕 What is the new behavior (if this is a feature change)?

Common code for pagination is injected with a derive macro, rather than implemented wherever required.

💥 Does this PR introduce a breaking change?

No.

🤔 Checklist before submitting

• All projects build
• Follows style guide lines
• Relevant documentation was updated
• Rebased onto current main

[tluijken]

2 vragen die wellicht buiten scope van deze PR vallen:

• Kunnen we de paginatable trait weghalen? Nu moet je een extra using toevoegen:

use stellar_rust_sdk_derive::Pagination;
use stellar_rs::Paginatable;  // deze mag wat mij betreft komen te vervallen

Kunnen we met de derive trait ook members aan de struct toevoegen?

Verder ziet het er logisch uit.

[tluijken]

Onderzoeksvraagje: kunnen we ook members aan een struct toevoegen middels de DeriveMacro?