1124 viewers are not allowed in rotations (#1577)

# What this PR does
Added additional filtering for roles 0 and 1 for rodations. Only Editors
and Admins are allowed to be in rotation

## Which issue(s) this PR fixes
https://github.com/grafana/oncall/issues/1124

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Updated wording throughout plugin to use 'Alert Group' instead of 'Incident' ([1565](https://github.com/grafana/oncall/pull/1565),
   [1576](https://github.com/grafana/oncall/pull/1576))
+- Filtering for Editors/Admins was added to rotation form. It is not allowed to assign Viewer to rotation ([1124](https://github.com/grafana/oncall/issues/1124))
 
 ### Fixed
 

grafana-plugin/src/components/UserGroups/UserGroups.tsx

@@ -110,7 +110,7 @@ const UserGroups = (props: UserGroupsProps) => {
           key={items.length}
           showSearch
           placeholder="Add user"
-          href="/users/?filters=true"
+          href="/users/?roles=0&roles=1&filters=true"
           value={null}
           onChange={handleUserAdd}
           showError={showError}