feat: Add NonZeroUuid type for optimized Option<Uuid> representation

[ab22593k]

This commit introduces a new NonZeroUuid type that wraps a Uuid and guarantees that it is not the nil UUID. This allows for a more memory-efficient representation of Option<Uuid>, as Option<NonZeroUuid> takes up the same space as Uuid.

This change improves the memory efficiency of representing optional UUIDs and provides a more convenient way to work with non-nil UUIDs.

fixes: #770

[KodrAus]

Thanks for the PR @ab22593k! I've left a few comments to get started.

In addition to this, I think we should consider other trait implementations on this type:

• Debug and Display that are based on the underlying Uuid
• serde::Serialize and other external libraries that uuid optionally depends on

I'd also like to set the expectation that we won't be adding any methods to NonNilUuid besides construction from Uuids and conversions to Uuids, otherwise it'll end up duplicating Uuids entire API on it.

It's also worth pointing out that the conversion will always succeed for any Uuid created via the Uuid::new_v* methods, since they set version/variant bits they're never nil.

[ab22593k]

PTL @KodrAus

[KodrAus]

It looks like we've got some build failures with different feature combinations:

Compiling proc-macro2 v1.0.93
     Compiling toml_edit v0.22.22
     Compiling quote v1.0.38
     Compiling syn v2.0.96
     Compiling toml v0.8.19
     Compiling serde_derive v1.0.217
     Compiling trybuild v1.0.101
     Compiling uuid v1.11.1 (/home/runner/work/uuid/uuid)
  error[E0599]: no function or associated item named `new_v4` found for struct `Uuid` in the current scope
     --> src/non_nil.rs:73:26
      |
  73  |         let uuid = Uuid::new_v4();
      |                          ^^^^^^ function or associated item not found in `Uuid`
      |
     ::: src/lib.rs:453:1
      |
  453 | pub struct Uuid(Bytes);
      | --------------- function or associated item `new_v4` not found for this struct
      |
  note: if you're trying to build a new `Uuid` consider using one of the following associated functions:
        builder::<impl Uuid>::nil
        builder::<impl Uuid>::max
        builder::<impl Uuid>::from_fields
        builder::<impl Uuid>::from_fields_le
        and 10 others
     --> src/builder.rs:72:5
      |
  72  |     pub const fn nil() -> Self {
      |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
  ...
  98  |     pub const fn max() -> Self {
      |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
  ...
  122 |     pub const fn from_fields(d1: u32, d2: u16, d3: u16, d4: &[u8; 8]) -> Uuid {
      |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  ...
  168 |     pub const fn from_fields_le(d1: u32, d2: u16, d3: u16, d4: &[u8; 8]) -> Uuid {
      |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

[ab22593k]

We should use Uuid::builder() since the new_v4 method is not available.

[KodrAus]

Thanks for working through this @ab22593k! I just had a few comments, but I think this is getting close now.

[KodrAus]

Thanks @ab22593k! This looks good to me