Ruby 2.7 introduced [numbered block parameters][], and 3.0 introduced
[Hash literal value omission][], so document how they integrate with
Factory Bot.

[numbered block parameters]: https://ruby-doc.org/core-2.7.1/Proc.html#class-Proc-label-Numbered+parameters
[Hash literal value omission]: https://docs.ruby-lang.org/en/3.1/syntax/literals_rdoc.html#label-Hash+Literals

fixes #1498
closes #1514

Co-authored-by: Alexandre Ruban <alexandre@hey.com>

RSpec's `expect` has two forms:

- scalar: `expect(result).to be_truthy`
- block: `expect { thunk }.not_to raise_error(RuntimeError)`

So what happens when you mix them?

```ruby
thunk = -> { 1 / 0 }
expect(thunk).not_to raise_error(RuntimeError)
```

If you do that, RSpec complains:

> The implicit block expectation syntax is deprecated, you should pass a
> block rather than an argument to `expect` to use the provided block
> expectation matcher or the matcher must implement
> `supports_value_expectations?`

The easy solution is to pass the Proc as a block, using `&`:

```
thunk = -> { 1 / 0 }
expect(&thunk).not_to raise_error(RuntimeError)
```

* Added: if `build_stubbed` detects a UUID primary key, generate the correct
  type (Peter Boling, Alexandre Ruban).
* Docs: show examples of Ruby 3 syntactic sugars (Sean Doyle).
* Internal: resolve test warning messages (Mike Burns).