Add quote response to the appropriate methods

[marcvdm]

https://dm.realtimeregister.com/docs/api/quotes

Added the quote responses to the domain methods.

Also make use of php enums instead of custom ones.
This could be reverted to use the internal enums but i thinks we should move them all to the new php enums.

Another thing i changed/added is making use of readonly properties and a public constructor.
This way an object in immutable and can safely be created with named arguments.

[codecov]

Codecov Report

Attention: 11 lines in your changes are missing coverage. Please review.

Comparison is base (834a68e) 98.77% compared to head (7d38b18) 98.32%.

❗ Current head 7d38b18 differs from pull request most recent head 4b9b51b. Consider uploading reports for the commit 4b9b51b to get more accurate results

Additional details and impacted files

@@             Coverage Diff              @@
##             master      #77      +/-   ##
============================================
- Coverage     98.77%   98.32%   -0.46%     
- Complexity      588      598      +10     
============================================
  Files           111      112       +1     
  Lines          2295     2324      +29     
============================================
+ Hits           2267     2285      +18     
- Misses           28       39      +11     

Files	Coverage Δ
src/Api/DomainsApi.php	100.00% <100.00%> (ø)
src/Domain/Billable.php	100.00% <100.00%> (ø)
src/Domain/DomainQuote.php	50.00% <50.00%> (ø)
src/Domain/Quote.php	50.00% <50.00%> (ø)

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[glenn1001]

@marcvdm Thank you for the PR, this will be merged to master any moment.
Later this week there will be some small additional changes and afterwards we will create a new release.

[ghost]

LGTM