Create factory methods in all API classes

[Art4]

Affected classes:

• Redmine\Api\Attachment
• Redmine\Api\CustomField
• Redmine\Api\Group
• Redmine\Api\Issue
• Redmine\Api\IssueCategory
• Redmine\Api\IssuePriority
• Redmine\Api\IssueRelation
• Redmine\Api\IssueStatus
• Redmine\Api\Membership
• Redmine\Api\News
• Redmine\Api\Project
• Redmine\Api\Query
• Redmine\Api\Role
• Redmine\Api\Search
• Redmine\Api\TimeEntry
• Redmine\Api\TimeEntryActivity
• Redmine\Api\Tracker
• Redmine\Api\User
• Redmine\Api\Version
• Redmine\Api\Wiki

Closes #368

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.32%. Comparing base (00d823f) to head (0ab0d20).

Additional details and impacted files

@@             Coverage Diff              @@
##               v2.x     #458      +/-   ##
============================================
- Coverage     98.52%   98.32%   -0.20%     
- Complexity      661      691      +30     
============================================
  Files            29       29              
  Lines          2031     2091      +60     
============================================
+ Hits           2001     2056      +55     
- Misses           30       35       +5     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.