Macros, Conv: Handle edge cases, refactor macros

[lvkv]

Three commits:

1. A macro refactor to move as much logic out of the pam_hooks macro and into "normal" functions that can be tested more easily
2. A fix for Conv::send so that it rejects unsupported PAM message styles; also removes support for the binary message style because the send internals assume strings, not arbitrary bytes.
3. Handle the edge case of the PAM handle pointer itself being null

[Copilot]

Pull request overview

Refactors the PAM hook entrypoint macro to centralize safety/validation logic in testable functions, and hardens the conversation (Conv) API by rejecting unsupported PAM message styles (including binary prompts) while also handling a null PAM handle pointer edge case.

Changes:

• Refactor pam_hooks! to call a shared invoke_hook helper that validates pamh/argc/argv and panic-guards hook execution.
• Update Conv::send to reject unsupported/unknown message styles and drop binary prompt support.
• Make PAM_BINARY_PROMPT non-public (crate-only) since it’s not supported by send.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
pam/src/macros.rs	Moves hook invocation/validation into invoke_hook, updates hook entrypoints to accept raw pamh pointer, adds/updates unit tests.
pam/src/conv.rs	Adds message-style validation to Conv::send and introduces tests for rejected styles and invalid input.
pam/src/constants.rs	Restricts PAM_BINARY_PROMPT visibility to pub(crate) to reflect unsupported status.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.