[#491] Ensure enum string literals are null terminated

[orecham]

Notes for Reviewer

Fix bug where string literals were not null terminated.

Unrelated: Also fix typo in existing assert_that message.

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1. Add sensible notes for the reviewer
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   • Commit messages have the issue ID ([#123] Add posix ipc example)
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References

Closes #491

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Project coverage is 79.10%. Comparing base (949d2e0) to head (32e86bd).

Files with missing lines	Patch %	Lines
iceoryx2-bb/derive-macros/src/lib.rs	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #538      +/-   ##
==========================================
- Coverage   79.13%   79.10%   -0.04%     
==========================================
  Files         202      202              
  Lines       24815    24819       +4     
==========================================
- Hits        19638    19632       -6     
- Misses       5177     5187      +10     

Files with missing lines	Coverage Δ
iceoryx2-bb/derive-macros/src/lib.rs	0.00% <0.00%> (ø)

... and 9 files with indirect coverage changes

[elfenpiff]

Oh I also run into this issue.

[elfenpiff]

In rust strings are never null terminated it is only typical for ffi bindings. Should we move string_literal_derive into iceoryx2-ffi since it is only used there?

[elBoberido]

Suggested change

	/// assert_eq!(v1.as_str_literal(), "custom variant one\0");
	/// assert_eq!(v1.as_str_literal(), c"custom variant one");

Can the same be made in the macro? Something like c#enum_string_literal