Resolve "Use prometheus' default securityContext"

Closes #305

See merge request openappstack/openappstack!97

Helm 2.14.3 updated nextcloud

Closes #338 and #334

See merge request openappstack/openappstack!100

Merge branch '305-use-prometheus-default-securitycontext' of open.greenhost.net:openappstack/openappstack into 305-use-prometheus-default-securitycontext

Merge remote-tracking branch 'origin/333-update-nextcloud-onlyoffice-version' into helm_2.14.3_updated_nextcloud

We got an `Error: unsupported format` with an auto-updated Helm `2.15.0`
installed from snap.
Now we pin it to a specific working version and use the official install script.

Resolve "Fix `CoreDnsDown` prometheus alert"

Closes #337

See merge request openappstack/openappstack!98

Resolve "behave test fails with non-english localisation"

Closes #208

See merge request openappstack/openappstack!96

Resolve "Remove requirements.lock file"

Closes #334

See merge request openappstack/openappstack!95

Resolve "Update documentation to match new openappstack cli"

Closes #297 and #328

See merge request openappstack/openappstack!88

Resolve "Can't save nextcloud email settings"

Closes #320

See merge request openappstack/openappstack!90

Resolve "Add option to `create` OAS on non-greenhost VPS"

Closes #317

See merge request openappstack/openappstack!89

Resolve "Allow custom rke config options"

Closes #321

See merge request openappstack/openappstack!91

Closes: #321