Add CodamaPdaHelpers derive

[grod220]

Adds #[derive(CodamaPdaHelpers)] which generates runtime PDA helper methods from existing #[codama(seed(...))] attributes. This reduces repeated manual PDA boilerplate program devs are writing.

API

use codama::{CodamaPda, CodamaPdaHelpers};

#[derive(CodamaPda, CodamaPdaHelpers)]
#[codama(seed(type = string(utf8), value = "mint"))]
#[codama(seed(name = "unwrappedMint", type = public_key))]
#[codama(seed(name = "wrappedTokenProgram", type = public_key))]
pub struct WrappedMintPda;

// ==== In program ==== 

let (address, bump) = WrappedMintPda::derive_program_address(
    &unwrapped_mint,
    &wrapped_token_program,
    &program_id,
)?;

let signer_seeds: [Seed; 4] = WrappedMintPda::signer_seeds(
    &unwrapped_mint,
    &wrapped_token_program,
    &bump_bytes,
);

• Implemented macro expansion that parses struct-level #[codama(seed(...))] directives and generates:
  • seeds
  • seeds_with_bump
  • signer_seeds
  • (wrapping Address methods below)
  • derive_address
  • create_program_address
  • find_program_address
  • try_find_program_address
  • derive_program_address
• Supports constant seeds (string(utf8), integer number(...)) and variable/linked seeds
• Handles seed name deduplication, identifier collision detection, reserved bump, and Rust keyword escaping

Discussion points

• Better name?
• Should all of those Address methods be shipped? Aka, should we drop find_program_address?
• The intention was for program usage, but might clients also need this?
• An impl vs external crate helpers
• How does this sit next to the CPI helpers PR (link?)

[grod220]

@febo better naming proposals?

[lorisleiva]

Whatever we land on with the derive name, just want to flag that IMO it should start with Codama since it purely relies on codama attributes.

[grod220]

@febo thoughts on which Address methods this should include? This sort of wraps everything, but maybe it should be a blessed subset.

[lorisleiva]

I'll go through this thoroughly asap but I just wanted to share some early first impression feedback.

[lorisleiva]

Since we already have an exported CamelCaseString struct in codama-nodes maybe it would be cleaner / more consistent to also add a SnakeCaseString struct there instead of introducing a new dependency.

[lorisleiva]

It would be nice if this macro was on its own crate. Maybe something like codama-pda-helpers or whatever the name ends up being here.

That way, if anyone wants to use a slightly different version of our generated code, it's easier for them to fork that crate on its own.