`DEVELOPMENT.md` sample functions (`load_payment`, `migrate`, `PaymentRecordV1`) don't exist

[therealjhay]

ProblemThe guide's worked examples reference symbols that are absent from the codebase, making it impossible to follow literally.

1. Non-existent symbols.
2. Guide unusable as written.
3. Doc debt.

Solution

• Either implement the examples or rewrite the guide around real functions.

Acceptance Criteria

• Guide references only existing code.
• cargo test --workspace passes.

Note for Contributors: Write a clear PR description. Show the corrected guide.

[Chigybillionz]

Hi, I’ve reviewed this issue and I’m confident I can fix it. I’d like to take it on.

[grantfox-oss]

🦊 GrantFox — @Chigybillionz has been assigned to this issue as part of the Third Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #574)
2. Your PR will be reviewed by the Betta-Pay maintainers

Good luck! Track your progress on GrantFox.