fix: Standardize email field editable to system-but-optional (#24416)

Change email booking field's editable property from 'system' to
'system-but-optional' across all code paths. This allows email field
to be optional when phone field is required instead.

- Updated systemBeforeFieldEmail in API v2024_06_14 transformers
- Fixed explicit override in API v2024_04_15 service
- Updated test utility to match production behavior
- Ensures consistency with validation logic that requires either
  email OR phone to be visible and required

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/api/v2/src/ee/event-types/event-types_2024_04_15/services/event-types.service.ts

@@ -137,7 +137,11 @@ export class EventTypesService_2024_04_15 {
       !bookingFields.find((field) => field.type === "email") &&
       !bookingFields.find((field) => field.type === "phone")
     ) {
-      bookingFields.push({ ...systemBeforeFieldEmail, type: BaseField.email, editable: Editable.system });
+      bookingFields.push({
+        ...systemBeforeFieldEmail,
+        type: BaseField.email,
+        editable: Editable.systemButOptional,
+      });
     }
 
     await updateEventType({

apps/api/v2/src/ee/event-types/event-types_2024_06_14/transformers/internal-to-api/booking-fields.ts

@@ -556,7 +556,7 @@ export const systemBeforeFieldEmail: EmailSystemField = {
   type: "email",
   name: "email",
   required: true,
-  editable: "system",
+  editable: "system-but-optional",
   sources: [
     {
       label: "Default",

apps/web/test/utils/bookingScenario/bookingScenario.ts

@@ -2397,7 +2397,7 @@ export const getDefaultBookingFields = ({
           label: "",
           hidden: false,
           sources: [{ id: "default", type: "default", label: "Default" }],
-          editable: "system",
+          editable: "system-but-optional",
           required: true,
           placeholder: "",
           defaultLabel: "email_address",