[Task] Allow arbitrary verification methods

[eike-hass]

Description

Allow setting and retrieving arbitrary verification method with no explicit support in the library.

Motivation

Allow implementers to utilize arbitrary verification methods with needing to extend the library.

Resources

Link to any resources relevant for the task such as issues, PRs, reference implementations, or specifications.

Change checklist

Add an x to the boxes that are relevant to your changes, and delete any items that are not.

• The feature or fix is implemented in Rust and across all bindings whereas possible.
• The feature or fix has sufficient testing coverage
• All tests and examples build and run locally as expected
• Every piece of code has been document according to the documentation guidelines.
• If conceptual documentation (mdbook) and examples highlighting the feature exist, they are properly updated.
• If the feature is not currently documented, a documentation task Issue has been opened to address this.