Ubuntu 20.04 support

Officially support and recommend Ubuntu 20.04 Focal.
The only tangible change is bumping the Vagrant box from 18.04 to 20.04.
Trellis has been made compatible with 20.04 already.

CHANGELOG.md

@@ -1,4 +1,5 @@
 ### HEAD
+* Officially support Ubuntu 20.04 (and default Vagrant to it) ([#1197](https://github.com/roots/trellis/pull/1197))
 
 ### 1.6.0: November 5th, 2020
 * Remove prestissimo for Composer 2.0 support ([#1247](https://github.com/roots/trellis/pull/1247))

roles/common/tasks/main.yml

@@ -67,7 +67,9 @@
 - name: Validate Ubuntu version
   debug:
     msg: |
-      Trellis is built for Ubuntu 18.04 Bionic as of https://github.com/roots/trellis/pull/992
+      Ubuntu 18.04 Bionic is the minimum supported version of Ubuntu in Trellis 1.0+ (as of https://github.com/roots/trellis/pull/992)
+
+      20.04 Focal is the recommend version for Trellis 1.7+ (as of https://github.com/roots/trellis/pull/1197)
 
       Your Ubuntu version is {{ ansible_distribution_version }} {{ ansible_distribution_release }}
 
@@ -77,8 +79,8 @@
 
       Development via Vagrant: `vagrant destroy && vagrant up`
 
-      Staging/Production: Create a new server with Ubuntu 18.04 and provision
-  when: ansible_distribution_release != 'bionic'
+      Staging/Production: Create a new server with Ubuntu 20.04 and provision
+  when: ansible_distribution_version is version('18.04', '<')
 
 - name: Check whether passlib is needed
   fail:

vagrant.default.yml

@@ -2,7 +2,7 @@
 vagrant_ip: '192.168.50.5'
 vagrant_cpus: 1
 vagrant_memory: 1024 # in MB
-vagrant_box: 'bento/ubuntu-18.04'
+vagrant_box: 'bento/ubuntu-20.04'
 vagrant_box_version: '>= 201807.12.0'
 vagrant_ansible_version: '2.8.0'
 vagrant_skip_galaxy: false