change maxUnavailable to integer (#535)

change maxUnavailable from `null` to `integer` to enable upgrade from
0.11.0 to 0.12.0 when using the specific variable.

* Also allow null value

Co-authored-by: Theron Voran <tvoran@users.noreply.github.com>

* add test for server.ha.disruptionBudget.maxUnavailable

Co-authored-by: Theron Voran <tvoran@users.noreply.github.com>

test/unit/server-ha-disruptionbudget.bats

@@ -85,3 +85,15 @@ load _helpers
       yq '.spec.maxUnavailable' | tee /dev/stderr)
   [ "${actual}" = "2" ]
 }
+
+@test "server/DisruptionBudget: correct maxUnavailable with custom value" {
+  cd `chart_dir`
+  local actual=$(helm template \
+      --show-only templates/server-disruptionbudget.yaml  \
+      --set 'server.ha.enabled=true' \
+      --set 'server.ha.replicas=3' \
+      --set 'server.ha.disruptionBudget.maxUnavailable=2' \
+      . | tee /dev/stderr |
+      yq '.spec.maxUnavailable' | tee /dev/stderr)
+  [ "${actual}" = "2" ]
+}

values.schema.json

@@ -484,7 +484,10 @@
                                     "type": "boolean"
                                 },
                                 "maxUnavailable": {
-                                    "type": "null"
+                                    "type": [
+                                        "null",
+                                        "integer"
+                                    ]
                                 }
                             }
                         },