Prevent unsupported classes from being added

app/models/ext_management_system.rb

@@ -37,7 +37,7 @@ def self.supported_types_for_create
   end
 
   def self.supported_for_create?
-    !reflections.include?("parent_manager")
+    ExtManagementSystem.supported_types_and_descriptions_hash.key?(ems_type) && !reflections.include?("parent_manager")
   end
 
   belongs_to :provider

spec/models/ext_management_system_spec.rb

@@ -126,6 +126,16 @@
     expect(ems.total_storages).to eq 2
   end
 
+   context "supported_for_create?" do
+    it "base class is unsupported" do
+      expect(FactoryBot.create(:ext_management_system).class.supported_for_create?).to eq(false)
+    end
+
+    it "supported class is supported" do
+      expect(FactoryBot.create(:ems_vmware).class.supported_for_create?).to eq(true)
+    end
+  end
+
   context "#hostname / #hostname=" do
     it "will delegate to the default endpoint" do
       ems = FactoryBot.build(:ems_vmware, :hostname => "example.org")