Merge branch 'coffeescript-coverage' into 'master'

Add JavaScript coverage analysis

## What does this MR do?

- configure teaspoon to calculate test coverage of JavaScript files
- publish result as GitLab pages

## Why was this MR needed?

- test coverage was not calculated for JavaScript files
- JavaScript wants to be under cover  

## What are the relevant issue numbers?

#19412 

See merge request !5052

.gitignore

@@ -30,6 +30,7 @@
 /config/secrets.yml
 /config/sidekiq.yml
 /coverage/*
+/coverage-javascript/
 /db/*.sqlite3
 /db/*.sqlite3-journal
 /db/data.yml

.gitlab-ci.yml

@@ -222,7 +222,15 @@ teaspoon:
   stage: test
   <<: *use-db
   script:
+    - curl --silent --location https://deb.nodesource.com/setup_6.x | bash -
+    - apt-get install --assume-yes nodejs
+    - npm install --global istanbul
     - teaspoon
+  artifacts:
+    name: coverage-javascript
+    expire_in: 31d
+    paths:
+    - coverage-javascript/default/
 bundler:audit:
   stage: test
@@ -269,10 +277,12 @@ pages:
   stage: pages
   dependencies:
     - coverage
+    - teaspoon
   script:
     - mv public/ .public/
     - mkdir public/
     - mv coverage public/coverage-ruby
+    - mv coverage-javascript/default/ public/coverage-javascript/
   artifacts:
     paths:
       - public

spec/teaspoon_env.rb

@@ -149,7 +149,7 @@ Teaspoon.configure do |config|
   # Specify that you always want a coverage configuration to be used. Otherwise, specify that you want coverage
   # on the CLI.
   # Set this to "true" or the name of your coverage config.
-  # config.use_coverage = nil
+  config.use_coverage = true
   # You can have multiple coverage configs by passing a name to config.coverage.
   # e.g. config.coverage :ci do |coverage|
@@ -158,15 +158,15 @@ Teaspoon.configure do |config|
     # Which coverage reports Istanbul should generate. Correlates directly to what Istanbul supports.
     #
     # Available: text-summary, text, html, lcov, lcovonly, cobertura, teamcity
-    # coverage.reports = ["text-summary", "html"]
+    coverage.reports = ["text-summary", "html"]
     # The path that the coverage should be written to - when there's an artifact to write to disk.
     # Note: Relative to `config.root`.
-    # coverage.output_path = "coverage"
+    coverage.output_path = "coverage-javascript"
     # Assets to be ignored when generating coverage reports. Accepts an array of filenames or regular expressions. The
     # default excludes assets from vendor, gems and support libraries.
-    # coverage.ignore = [%r{/lib/ruby/gems/}, %r{/vendor/assets/}, %r{/support/}, %r{/(.+)_helper.}]
+    coverage.ignore = [%r{vendor/}, %r{spec/}]
     # Various thresholds requirements can be defined, and those thresholds will be checked at the end of a run. If any
     # aren't met the run will fail with a message. Thresholds can be defined as a percentage (0-100), or nil.