Merge branch 'update-nginx-config-for-websockets' into 'master'

Update NGINX configuration files to add websocket support

## What does this MR do?

Changes the bundled NGINX configuration files to support websockets introduced in https://gitlab.com/gitlab-org/gitlab-workhorse/merge_requests/83

These changes are also going into omnibus: https://gitlab.com/gitlab-org/omnibus-gitlab/merge_requests/1146

## Are there points in the code the reviewer needs to double check?

Best to wait until the omnibus MR is merged as the method may be changed.

## Why was this MR needed?

Without it, NGINX won't let websockets through to workhorse.

## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- Tests
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [X] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [X] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?

Related to #22864

See merge request !8039

lib/support/nginx/gitlab

@@ -20,6 +20,11 @@ upstream gitlab-workhorse {
   server unix:/home/git/gitlab/tmp/sockets/gitlab-workhorse.socket fail_timeout=0;
 }
 
+map $http_upgrade $connection_upgrade_gitlab {
+    default upgrade;
+    ''      close;
+}
+
 ## Normal HTTP host
 server {
   ## Either remove "default_server" from the listen line below,
@@ -53,6 +58,8 @@ server {
     proxy_set_header    X-Real-IP           $remote_addr;
     proxy_set_header    X-Forwarded-For     $proxy_add_x_forwarded_for;
     proxy_set_header    X-Forwarded-Proto   $scheme;
+    proxy_set_header    Upgrade             $http_upgrade;
+    proxy_set_header    Connection          $connection_upgrade_gitlab;
 
     proxy_pass http://gitlab-workhorse;
   }

lib/support/nginx/gitlab-ssl

@@ -24,6 +24,11 @@ upstream gitlab-workhorse {
   server unix:/home/git/gitlab/tmp/sockets/gitlab-workhorse.socket fail_timeout=0;
 }
 
+map $http_upgrade $connection_upgrade_gitlab_ssl {
+    default upgrade;
+    ''      close;
+}
+
 ## Redirects all HTTP traffic to the HTTPS host
 server {
   ## Either remove "default_server" from the listen line below,
@@ -98,6 +103,9 @@ server {
     proxy_set_header    X-Forwarded-Ssl     on;
     proxy_set_header    X-Forwarded-For     $proxy_add_x_forwarded_for;
     proxy_set_header    X-Forwarded-Proto   $scheme;
+    proxy_set_header    Upgrade             $http_upgrade;
+    proxy_set_header    Connection          $connection_upgrade_gitlab_ssl;
+
     proxy_pass http://gitlab-workhorse;
   }