resolve #642 - Add Pattern Matching

[baweaver]

Resolves feature request #642 requesting the addition of Pattern
Matching hooks for Ruby 2.7+ by introducing to_h, deconstruct, and
deconstruct_keys to core classes.

This change also addresses spec changes by gating pattern matching specs
on Ruby 2.7+ to prevent failures in older versions. All specs have also
been given a pattern matching spec matching their implementation to
demonstrate potential usages.

While demonstrational usages could dive into nested classes that are in
HTTP this was avoided to keep tests isolated from eachother.

Examples of what this makes possible, among other things:

response = HTTP.get('https://jsonplaceholder.typicode.com/users')

# Array style

# Right-hand assignment
response => [status, _, body]

# Body is _long_
p status: status, body_size: body.size
# => {:status=>200, :body_size=>5645}

case response
in 200, _, body
  body.size
else
  false
end
# => 5645

# Hash style

case response
in {
  status: 200,
  body: {
    contents:  /address/ => contents,
    streaming: false,
    encoding:  Encoding::UTF_8
  },
  headers: {
    content_type: /json/,
    server:       'cloudflare'
  }
}
  [true, contents.size]
else
  [false, nil]
end
# => [true, 5645]

[baweaver]

It appears that conditional gating for Ruby 2.7+ isn't isolating these specs. I'll have to follow up with an additional commit some time tomorrow when I have time to address that.

[baweaver]

This may be unnecessary if an alternate method is available that does the same.

[baweaver]

The only way I can get around "invalid" syntax that doesn't exist until 2.7 that I can think of or get to work is unfortunately very hacky:

if RUBY_VERSION >= '2.7'
  eval <<~RUBY
    [1,2,3] in [1, *]
  RUBY
end

Would love to implement this for newer versions of Ruby but can't think of anything better than that hack for the moment

[baweaver]

It appears that Ruby core uses a similar hack to get around old versions:

ruby/ruby@f9696ca

[baweaver]

Regarding CodeClimate I can reduce one of the methods out, but the other class not as easily. Granted my opinion is 20 methods / class is a bit arbitrary, but will defer to standards of the repo.