feat(enum): add basic enum support

[Xenira]

Fixes: #178
Refs: #302

Description

PHP 8.1 introduced enums. This is a migration of #302 to the new macro system.

MR is currently incomplete, but the basic case already works.

I feature guarded this behind the enum feature. As I added this to the default features this is a soft bump of the minimum supported PHP version. Setting default-features to false will still allow 8.0 though.

Progress

• Register unit enums
• Register backed enums
• Enums as return types (IntoZval)
• Enums as parameters (FromZval)
• TryFrom for backed enums
• Stubs
• Tests
• Documentation

Checklist

Check the boxes that apply (put an x in the brackets, like [x]). You can also check boxes after the PR is created.

• I have read the contribution guidelines.
• I have added tests that prove my code works as expected.
• I have added documentation if applicable.
• I have added a migration guide if applicable.

❤️ Thank you for your contribution!

[coveralls]

Pull Request Test Coverage Report for Build 16401140698

Details

• 118 of 288 (40.97%) changed or added relevant lines in 7 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+1.2%) to 26.945%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
crates/macros/src/lib.rs	2	5	40.0%
src/describe/mod.rs	1	8	12.5%
src/builders/module.rs	0	17	0.0%
src/describe/stub.rs	0	19	0.0%
src/enum_.rs	9	29	31.03%
src/builders/enum_builder.rs	14	47	29.79%
crates/macros/src/enum_.rs	92	163	56.44%

Files with Coverage Reduction	New Missed Lines	%
src/builders/module.rs	1	40.0%

Totals
Change from base Build 16394070386:	1.2%
Covered Lines:	1115
Relevant Lines:	4138

---

💛 - Coveralls

[Xenira]

@ptondereau thoughts?

Want to finalise the api before tackling the test.

[ptondereau]

This is a good feature! Thanks for the implementation.
Leaved some nitpicks.

[joehoyle]

Great stuff thanks @Xenira