Merge branch 'mysql-sources-utf8mb4-fix' into 'master'

Gitlab from sources : proper utf8mb4 support for MySQL 5.5 to 5.7

See merge request !8508

config/database.yml.mysql

@@ -3,8 +3,8 @@
 #
 production:
   adapter: mysql2
-  encoding: utf8mb4
-  collation: utf8mb4_general_ci
+  encoding: utf8
+  collation: utf8_general_ci
   reconnect: false
   database: gitlabhq_production
   pool: 10
@@ -18,8 +18,8 @@ production:
 #
 development:
   adapter: mysql2
-  encoding: utf8mb4
-  collation: utf8mb4_general_ci
+  encoding: utf8
+  collation: utf8_general_ci
   reconnect: false
   database: gitlabhq_development
   pool: 5

doc/update/8.15-to-8.16.md

@@ -97,6 +97,8 @@ sudo -u git -H bundle exec rake db:migrate RAILS_ENV=production
 sudo -u git -H bundle exec rake assets:clean assets:precompile cache:clear RAILS_ENV=production
 ```
 
+**MySQL installations**: Run through the `MySQL strings limits` and `Tables and data conversion to utf8mb4` [tasks](../install/database_mysql.md).
+
 ### 6. Update gitlab-workhorse
 
 Install and compile gitlab-workhorse. This requires