Similar to https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/31834,
we see that in https://gitlab.com/gitlab-org/gitlab-ce/issues/65957
there can be hundreds, even thousands, of Gitaly requests in the
`/api/:version/projects/:id/merge_requests/:noteable_id/notes` endpoint.

Previously, the API to retrieve notes generated hundreds of Gitaly calls
to determine whether a system note should be shown to the user. It did
this by:

1. Rendering the Markdown
2. Extracting cross-references from the Markdown
3. Issuing a Gitaly `FindCommit` RPC for every reference to validate
that the commit exists.

The last step is unnecessary because we don't need to display a commit
if the user doesn't have access to the project in the first place.
`RendersNotes#prepare_notes_for_rendering` is already used in
`MergeRequestsController`, which is why we don't see N+1 Gitaly calls
there. We use it here to optimize the note redaction process.

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

Updates specs to use new rails5 format.

The old format:
`get :show, { some: params }, { some: headers }`

The new format:
`get :show, params: { some: params }, headers: { some: headers }`

* adds basic discussions API for issues and snippets
* reorganizes notes specs (so same tests can be used for all noteable types - issues, MRs, snippets)

Removed all the unnecessary include of `WaitForAjax` and `ApiHelpers` in the specs.
Removed unnecessary usage of `api:true`

In API V4 all endpoints were changed so Merge Requests and Issues
should be referred by iid, instead of id. Except the /notes endpoint
was forgotten. So change the endpoints from:

- /projects/:id/issues/:issue_id/notes
- /projects/:id/merge_requests/:merge_request_id/notes

To:

- /projects/:id/issues/:issue_iid/notes
- /projects/:id/merge_requests/:merge_request_iid/notes

For Project Snippets nothing changes.

add /award slash command; Allow posting of just an emoji in comment

This reverts commit cb10b725c8929b8b4460f89c9d96c773af39ba6b.

Prevent users from creating notes on resources they can't access

See https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/2054

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

Restore changes for api spec files

Fix error in rspec Users

Delete extra space Repositories-spec

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

The amount of precision times have in databases is variable, so we need
tolerances when comparing in specs. It's better to have the tolerance defined
in one place than several.

This reverts commit 3e991230.