Merge branch 'master' into 38869-datetime

* master: (112 commits)
  small change to make less conflict with EE version
  Add cop for use of remove_column
  Resolve merge conflicts with dev.gitlab.org/master after security release
  add index for doc/administration/operations/
  Remove RubySampler#sample_objects for performance as well
  Bugfix: User can't change the access level of an access requester
  Add spec for removing issues.assignee_id
  updated imports
  Keep track of storage check timings
  Remove a header level in the new 'Automatic CE->EE merge' doc
  Improve down step of removing issues.assignee_id column
  Fix specs after removing assignee_id field
  Remove issues.assignee_id column
  Resolve conflicts in app/models/user.rb
  Fix image view mode
  Do not raise when downstream pipeline is created
  Remove the need for destroy and add a comment in the spec
  Use build instead of create in importer spec
  Simplify normalizing of paths
  Remove allocation tracking code from InfluxDB sampler for performance
  ...