Create a Not expression

[hgraca]

This will reduce the amount of expressions needed
and allow for complex expressions (within an OR
or an AND) to be negated.

[fain182]

We already tried this, it would be nice because we could remove some rules, but the error messages are much less readable.
I think we should prioritize DX over our code simplicity...

[hgraca]

I understand, however, it's not just your code, it's also the code of the developers using this library.

1. There are rules that are specific to a project, and not really useful anywhere else, and developers could build just the positive version and negate it using the Not provided by the library;

2. There are complex and dynamic rules that we can't build if we don't have the Not, for example, the PR that you liked is not possible, or at least not elegantly, done without this.

3. From what I understand, your reservation is not about the rule, but about the feedback when it fails, so I would say it's a different issue to tackle, maybe for boolean expressions we should have a different way of composing the error message? I feel that must NOT (HappyIsland should be an interface) because we want to add this rule for our software is acceptable feedback for a developer to read as a tradeoff for using this expression, and it doesn't stop anyone from building specific NotFooBar expressions.

[codecov-commenter]

Codecov Report

Merging #394 (060d6fb) into main (976c200) will increase coverage by 0.04%.
The diff coverage is 100.00%.

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@@             Coverage Diff              @@
##               main     #394      +/-   ##
============================================
+ Coverage     94.33%   94.37%   +0.04%     
- Complexity      571      575       +4     
============================================
  Files            67       68       +1     
  Lines          1500     1512      +12     
============================================
+ Hits           1415     1427      +12     
  Misses           85       85              

Files Changed	Coverage Δ
src/Expression/Boolean/Not.php	100.00% <100.00%> (ø)