Ticket custom fields can be constant, i.e. no edits

config/models

@@ -171,6 +171,7 @@ WorkflowField
     type     WorkflowFieldType
     enm      WorkflowFieldEnumId Maybe
     required Bool
+    constant Bool
     -- filter   TicketStatusFilterId
 
     UniqueWorkflowField workflow ident

src/Vervis/Form/Workflow.hs

@@ -57,6 +57,7 @@ data NewField = NewField
     , nfDesc  :: Maybe Text
     , nfType  :: WorkflowFieldType
     , nfReq   :: Bool
+    , nfConst :: Bool
     }
 
 newFieldAForm :: WorkflowId -> AForm Handler NewField
@@ -66,6 +67,7 @@ newFieldAForm wid = NewField
     <*> aopt textField                 "Description" Nothing
     <*> areq (selectField optionsEnum) "Type*"       Nothing
     <*> areq checkBoxField             "Required*"   Nothing
+    <*> areq checkBoxField             "Constant*"   Nothing
 
 newFieldForm :: WorkflowId -> Form NewField
 newFieldForm wid = renderDivs $ newFieldAForm wid

src/Vervis/Handler/Workflow.hs

@@ -152,6 +152,7 @@ postWorkflowFieldsR shr wfl = do
                     , workflowFieldType     = nfType nf
                     , workflowFieldEnm      = Nothing
                     , workflowFieldRequired = nfReq nf
+                    , workflowFieldConstant = nfConst nf
                     }
             runDB $ insert_ field
             setMessage "Workflow field added."