Unlimited programs should be opened for users

[dchubar-fj]

Problem/Motivation
Classes with an unlimited number of spots are displayed as completely filled in Activity Finder with the Daxko back-end. The root of the problem is that Open Y doesn't check the limited flag in the Daxko response. Daxko back-end relies on the available field in the response:

         "availability":{
            "limited":true,
            "full":false,
            "max":20,
            "taken":0,
            "available":20,
            "has_waiting_list":false
         },

But unlimited classes don't have the available field:

         "availability":{
            "limited":false,
            "full":false,
            "taken":0,
            "has_waiting_list":true,
            "waiting_list_count":0,
            "show_waiting_list_count":false
         },

As result, unlimited classes are not available for registration in the Activity Finder, because the Register button is disabled

But they are open for registration in Daxko

Steps for review

• Find a class with unlimited spots in the Activity Finder with the Daxko back-end
• Check program details
• Verify the register button is not disabled

General checks

• All coding styles are fulfilled and there are no any issues reported by CodeSniffer. See Code of Conduct.
• Try to use Conventional commit messages accordingly to the standard https://www.conventionalcommits.org/en/v1.0.0/#specification
• Documentation has been updated according to PR changes.
• Steps for review have been provided according to PR changes.
  
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• Make sure your git email is associated with account on drupal.org, otherwise you won't get commits there.
  
• If you would like to get credits on drupal.org, check documentation.

Thank you for your contribution!

[podarok]

let's keep this as a constant of the current class, please

[podarok]

@dchubar-fj could you put your description in module's readme.md?
Thank you

[gundevel]

Build comment file:

Check Open Y Installation Wizard at http://install.openy.cibox.tools/build3277/install.php

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[gundevel]

Open Y Upgrade Path site check installed at http://upgrade.openy.cibox.tools/build3277/

[podarok]

Code looks good
Let's improve readme a bit @dchubar-fj

[gundevel]

Build comment file:

Check Open Y Installation Wizard at http://install.openy.cibox.tools/build3278/install.php

---

Test PASSed.
Refer to this link for build results (access rights to CI server needed):
http://openy.cibox.tools:8080/job/PR_BUILDER_COMPOSER/3278/

[gundevel]

Open Y Upgrade Path site check installed at http://upgrade.openy.cibox.tools/build3278/