Merge #1144

1144: Add proper release notes for 1.7 r=mergify[bot] a=kaiyou

## What type of PR?

Documentation

## What does this PR do?

When first writing the release notes, I forgot to include a proper release notes section in the docs.

### Related issue(s)

None

## Prerequistes
Before we can consider review and merge, please make sure the following list is done and checked.
If an entry in not applicable, you can check it or remove it from the list.

- [ ] In case of feature or enhancement: documentation updated accordingly
- [ ] Unless it's docs or a minor change: add [changelog](https://mailu.io/master/contributors/guide.html#changelog) entry file.


Co-authored-by: kaiyou <pierre@jaury.eu>

docs/releases.rst

@@ -1,6 +1,55 @@
 Release notes
 =============
 
+Mailu 1.7 - 2019-08-22
+----------------------
+
+Release 1.7 has come a long way and was really expected after the project first
+saw a slowdown in contributions around january then a wave of new contributors
+and contributions.
+
+New functionality
+`````````````````
+
+Most changes are internal, main features include:
+ - the admin UI now properly displaying on mobile
+ - relays supporting authentication thanks to new settings
+ - ability to create an initial admin user using environment variables
+
+Other changes include software updates with some new features in Rainloop
+1.30.0.
+
+Back-end
+````````
+
+One of the big tasks was upgradig to latest Alpine (3.10), which is now finished.
+Also, a lot was improved about the environment variables meant to provide
+specific hosts in custom setups.
+
+Finally, among many bug fixes and discrete enhancements, we removed most static
+assets from the repository and now build the admin UI dynamically using
+Webpack.
+
+Localization
+````````````
+
+The localization effort move to a hosted Weblate, that you can access at the
+following uri: https://translate.tedomum.net/projects/mailu/admin/
+
+Please have a look and help translate Mailu into your home tongue.
+
+Upgrading
+`````````
+
+Upgrade should run fine as long as you generate a new compose or stack
+configuration and upgrade your mailu.env.
+
+If you run the PostgreSQL server, the database was upgrade, so you will need to
+dump the database before upgrading and load the dump after the upgrade is
+complete. Please not that the shipped image for PostgreSQL database will be
+deprecated before 1.8.0, you can switch to an external database server by then.
+
+
 Mailu 1.6 - 2019-01-18
 ----------------------