Don't allow people to set their instance name to an empty string (or only whitespace) (#240)

* make server name required

* prevent space-only instance name

* add useTrimLead to TextFieldProps

web/components/config/form-textfield-with-submit.tsx

@@ -42,6 +42,7 @@ export default function TextFieldWithSubmit(props: TextFieldWithSubmitProps) {
     configPath = '',
     initialValue,
     useTrim,
+    useTrimLead,
     ...textFieldProps // rest of props
   } = props;
 
@@ -73,7 +74,7 @@ export default function TextFieldWithSubmit(props: TextFieldWithSubmitProps) {
     if (onChange) {
       onChange({
         fieldName: changedFieldName,
-        value: useTrim ? changedValue.trim() : changedValue,
+        value: useTrim ? changedValue.trim() : useTrimLead ? changedValue.replace(/^\s+/g,'') : changedValue,
       });
     }
   };

web/components/config/form-textfield.tsx

@@ -29,6 +29,7 @@ export interface TextFieldProps {
   tip?: string;
   type?: string;
   useTrim?: boolean;
+  useTrimLead?: boolean;
   value?: string | number;
   onBlur?: FieldUpdaterFunc;
   onChange?: FieldUpdaterFunc;