Mattermost Notifications Service

app/models/project.rb

app/models/project_services/chat_message/base_message.rb

app/models/project_services/chat_message/build_message.rb

app/models/project_services/chat_message/issue_message.rb

app/models/project_services/chat_message/merge_message.rb

app/models/project_services/chat_message/note_message.rb

app/models/project_services/chat_message/pipeline_message.rb

app/models/project_services/chat_message/push_message.rb

...models/project_services/chat_message/wiki_page_message.rb

app/models/project_services/chat_service.rb

app/models/project_services/mattermost_service.rb

...els/project_services/mattermost_slash_commands_service.rb

app/models/project_services/slack_service.rb

app/models/service.rb

changelogs/unreleased/issue_22269.yml

doc/api/services.md

doc/project_services/img/mattermost_configuration.png

doc/project_services/mattermost.md

doc/project_services/project_services.md

doc/project_services/slack.md