Redo internals of Incoming Mail Support

See merge request !9385

Fix the commit search UI

Closes gitlab-ee#1765

See merge request !9411

Upgrade Rails to 4.2.8

See merge request !9419

Rename retry failed button on pipeline page to just retry

See merge request !9369

Add user deletion permission check in `Users::DestroyService`

See merge request !8974

Changed coverage reg expression placeholder text to be more like a placeholder

Closes #28389

See merge request !9407

Hash concurrent foreign key names similar to Rails

See merge request !9415

Fix preselected namespace when creating a project

Closes #26879

See merge request !9389

Use POST methods to mark Todos as done

Closes #28467

See merge request !9410

Update using_docker_images.md

See merge request !9417

Added ability to change user permissions in group to owner

Closes #28233

See merge request !9299

Fixed alignment of snippet search results

Closes #26832

See merge request !9228

Signed-off-by: Rémy Coutable <remy@rymai.me>

This was initially not implemented simply because I forgot about the
size limit of constraint names in PostgreSQL (63 bytes). Using the old
technique we can't add foreign keys for certain tables. For example,
adding a foreign key on
protected_branch_merge_access_levels.protected_branch_id would lead to
the following key name:

    fk_protected_branch_merge_access_levels_protected_branches_protected_branch_id

This key is 78 bytes long, thus violating the PostgreSQL size
requirements.

The hashing strategy is copied from Rails' foreign_key_name() method,
which unfortunately is private and subject to change without notice.

Truncate long title text on Todo items

Closes #28186

See merge request !9311

Update GitLab CE/EE comparison & subscribe links in README.md

See merge request !9404

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/1765

Changes when loading indicator is added to dropdown

See merge request !9345

Allow searching issues for strings containing colons

Closes #28357

See merge request !9400

Add process for requesting approval for licenses

Closes gitlab-com/organization#22

See merge request !9242

Fix Spinach failure

See merge request !9401

Set dropdown height fixed to `250px;` and make it scrollable

Closes #26206

See merge request !9063

Rename karma job to rake karma

See merge request !9342

Resolve "Left align nav items"

Closes #27934

See merge request !9338

Fix issue where files on a fork could not be edited

Closes #28188

See merge request !9349

UX Guide: Add personas

See merge request !9390