t() calls should be avoided in classes and fixing dependency injection (current user and module handler)

Hey, found some best practice issues that I'll try to fix :), here's the list

vagrant@homestead:~/Code/d8/modules/contrib/google_analytics$ phpcs --standard=DrupalPractice --extensions=php,module,inc,install,test,profile,theme,info,txt,md .

FILE: ...Code/d8/modules/contrib/google_analytics/google_analytics.module
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FOUND 0 ERRORS AND 2 WARNINGS AFFECTING 2 LINES
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 10 | WARNING | @author tags are not usually used in Drupal, because
    |         | over time multiple contributors will touch the code
    |         | anyway
 28 | WARNING | Global constants should not be used, move it to a
    |         | class or interface
----------------------------------------------------------------------


FILE: ...b/google_analytics/src/Form/GoogleAnalyticsAdminSettingsForm.php
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FOUND 0 ERRORS AND 37 WARNINGS AFFECTING 31 LINES
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 136 | WARNING | \Drupal calls should be avoided in classes, use
     |         | dependency injection instead
 153 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 154 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 156 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 158 | WARNING | \Drupal calls should be avoided in classes, use
     |         | dependency injection instead
 159 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 160 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 161 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 164 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 195 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 196 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 221 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 222 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 223 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 274 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 274 | WARNING | \Drupal calls should be avoided in classes, use
     |         | dependency injection instead
 274 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 274 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 282 | WARNING | \Drupal calls should be avoided in classes, use
     |         | dependency injection instead
 324 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 324 | WARNING | \Drupal calls should be avoided in classes, use
     |         | dependency injection instead
 324 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 324 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 332 | WARNING | \Drupal calls should be avoided in classes, use
     |         | dependency injection instead
 401 | WARNING | \Drupal calls should be avoided in classes, use
     |         | dependency injection instead
 410 | WARNING | \Drupal calls should be avoided in classes, use
     |         | dependency injection instead
 457 | WARNING | \Drupal calls should be avoided in classes, use
     |         | dependency injection instead
 466 | WARNING | \Drupal calls should be avoided in classes, use
     |         | dependency injection instead
 488 | WARNING | \Drupal calls should be avoided in classes, use
     |         | dependency injection instead
 578 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 584 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 597 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 606 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 615 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 618 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 621 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
 624 | WARNING | t() calls should be avoided in classes, use
     |         | dependency injection and $this->t() instead
----------------------------------------------------------------------


FILE: .../modules/google_analytics_test/google_analytics_test.routing.yml
----------------------------------------------------------------------
FOUND 0 ERRORS AND 1 WARNING AFFECTING 1 LINE
----------------------------------------------------------------------
 7 | WARNING | Open page callback found, please add a comment before
   |         | the line why there is no access restriction
----------------------------------------------------------------------


FILE: ..._analytics_test/src/Controller/GoogleAnalyticsTestController.php
----------------------------------------------------------------------
FOUND 0 ERRORS AND 4 WARNINGS AFFECTING 4 LINES
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 20 | WARNING | Messages are user facing text and must run through
    |         | t() for translation
 21 | WARNING | Messages are user facing text and must run through
    |         | t() for translation
 22 | WARNING | Messages are user facing text and must run through
    |         | t() for translation
 23 | WARNING | Messages are user facing text and must run through
    |         | t() for translation
----------------------------------------------------------------------

Time: 365ms; Memory: 12Mb