feat: Send email from UI — inline reply composer & SendEmail mutation (#19363)

## Summary

- **Inline email reply**: Replace external email client redirects
(Gmail/Outlook deeplinks) with an in-app email composer. Users can reply
to email threads directly from the email thread widget or via the
command menu.
- **SendEmail GraphQL mutation**: New backend mutation that reuses
`EmailComposerService` for body sanitization, recipient validation, and
SMTP dispatch via the existing outbound messaging infrastructure.
- **Side panel compose page**: Command menu "Reply" action now opens a
side-panel compose email page with pre-filled To, Subject, and
In-Reply-To fields.

### Backend
- `SendEmailResolver` with `SendEmailInput` / `SendEmailOutputDTO`
- `SendEmailModule` wired into `CoreEngineModule`
- Reuses `EmailComposerService` + `MessagingMessageOutboundService`

### Frontend
- `EmailComposer` / `EmailComposerFields` components
- `useSendEmail`, `useReplyContext`, `useEmailComposerState` hooks
- `useOpenComposeEmailInSidePanel` + `SidePanelComposeEmailPage`
- `EmailThreadWidget` inline Reply bar with toggle composer
- `ReplyToEmailThreadCommand` now opens side-panel instead of external
links

### Seeds
- Added `handle` field to message participant seeds for realistic email
addresses
- Seed `connectedAccount` and `messageChannel` in correct batch order

## Test plan

- [ ] Open an email thread on a person/company record → verify
"Reply..." bar appears below the last message
- [ ] Click "Reply..." → composer opens inline with pre-filled To and
Subject
- [ ] Type a message and click Send → email is sent via SMTP, composer
closes
- [ ] Use command menu Reply action → side panel opens with compose
email page
- [ ] Verify Send/Cancel buttons work correctly in side panel
- [ ] Test with Cc/Bcc toggle in composer fields
- [ ] Verify error handling: invalid recipients, missing connected
account


Made with [Cursor](https://cursor.com)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

packages/twenty-server/src/engine/workspace-manager/dev-seeder/data/constants/message-participant-data-seeds.constant.ts

@@ -72,6 +72,7 @@ type ParticipantData = {
   workspaceMemberId: string;
   personId: string;
   displayName: string;
+  handle: string;
 };
 
 const GET_RANDOM_FAKE_PARTICIPANT = () => {
@@ -120,6 +121,7 @@ const CREATE_PERSON_PARTICIPANT = (
     workspaceMemberId: defaultWorkspaceMemberId,
     personId: PERSON_ID,
     displayName: `Person ${PERSON_INDEX}`,
+    handle: `person${PERSON_INDEX}@example.com`,
   };
 };
 
@@ -141,26 +143,30 @@ const CREATE_WORKSPACE_MEMBER_PARTICIPANT = (
     case WORKSPACE_MEMBER_DATA_SEED_IDS.TIM:
       return {
         workspaceMemberId: WORKSPACE_MEMBER_ID,
-        personId: personIds[0] || personIds[0],
+        personId: personIds[0],
         displayName: 'Tim Apple',
+        handle: 'tim@apple.dev',
       };
     case WORKSPACE_MEMBER_DATA_SEED_IDS.JONY:
       return {
         workspaceMemberId: WORKSPACE_MEMBER_ID,
         personId: personIds[1] || personIds[0],
         displayName: 'Jony Ive',
+        handle: 'jony@apple.dev',
       };
     case WORKSPACE_MEMBER_DATA_SEED_IDS.PHIL:
       return {
         workspaceMemberId: WORKSPACE_MEMBER_ID,
         personId: personIds[2] || personIds[0],
         displayName: 'Phil Schiller',
+        handle: 'phil@apple.dev',
       };
     default:
       return {
         workspaceMemberId: WORKSPACE_MEMBER_ID,
-        personId: personIds[0] || personIds[0],
+        personId: personIds[0],
         displayName: 'Workspace Member',
+        handle: 'member@apple.dev',
       };
   }
 };
@@ -176,6 +182,7 @@ const CREATE_FAKE_PARTICIPANT = (
     personId:
       personIds[Math.floor(Math.random() * Math.min(10, personIds.length))],
     displayName: FAKE.name,
+    handle: FAKE.email,
   };
 };
 
@@ -231,7 +238,6 @@ const CREATE_MESSAGE_PARTICIPANTS = (
     const ROLE = IS_SENDER
       ? MessageParticipantRole.FROM
       : MessageParticipantRole.TO;
-    const HANDLE = IS_SENDER ? 'outgoing' : 'incoming';
 
     // Random date within the last 3 months
     const NOW = new Date();
@@ -255,7 +261,7 @@ const CREATE_MESSAGE_PARTICIPANTS = (
       workspaceMemberId: PARTICIPANT_DATA.workspaceMemberId,
       personId: PARTICIPANT_DATA.personId,
       displayName: PARTICIPANT_DATA.displayName,
-      handle: HANDLE,
+      handle: PARTICIPANT_DATA.handle,
       role: ROLE,
       messageId,
     });

packages/twenty-server/src/engine/workspace-manager/dev-seeder/data/services/dev-seeder-data.service.ts

@@ -44,6 +44,14 @@ import {
   EMPLOYMENT_HISTORY_DATA_SEED_COLUMNS,
   EMPLOYMENT_HISTORY_DATA_SEEDS,
 } from 'src/engine/workspace-manager/dev-seeder/data/constants/employment-history-data-seeds.constant';
+import {
+  CONNECTED_ACCOUNT_DATA_SEED_COLUMNS,
+  CONNECTED_ACCOUNT_DATA_SEEDS,
+} from 'src/engine/workspace-manager/dev-seeder/data/constants/connected-account-data-seeds.constant';
+import {
+  MESSAGE_CHANNEL_DATA_SEED_COLUMNS,
+  MESSAGE_CHANNEL_DATA_SEEDS,
+} from 'src/engine/workspace-manager/dev-seeder/data/constants/message-channel-data-seeds.constant';
 import {
   MESSAGE_CHANNEL_MESSAGE_ASSOCIATION_DATA_SEED_COLUMNS,
   MESSAGE_CHANNEL_MESSAGE_ASSOCIATION_DATA_SEEDS,
@@ -157,9 +165,14 @@ const getRecordSeedsBatches = (
       pgColumns: DASHBOARD_DATA_SEED_COLUMNS,
       recordSeeds: getDashboardDataSeeds(workspaceId),
     },
+    {
+      tableName: 'connectedAccount',
+      pgColumns: CONNECTED_ACCOUNT_DATA_SEED_COLUMNS,
+      recordSeeds: CONNECTED_ACCOUNT_DATA_SEEDS,
+    },
   ];
 
-  // Batch 3: Depends on company and connectedAccount
+  // Batch 3: Depends on company, connectedAccount
   const batch3: RecordSeedConfig[] = [
     {
       tableName: 'person',
@@ -171,6 +184,11 @@ const getRecordSeedsBatches = (
       pgColumns: PET_DATA_SEED_COLUMNS,
       recordSeeds: PET_DATA_SEEDS,
     },
+    {
+      tableName: 'messageChannel',
+      pgColumns: MESSAGE_CHANNEL_DATA_SEED_COLUMNS,
+      recordSeeds: MESSAGE_CHANNEL_DATA_SEEDS,
+    },
   ];
 
   // Batch 4: Depends on person/company/messageChannel or independent

packages/twenty-server/src/engine/workspace-manager/twenty-standard-application/constants/standard-command-menu-item.constant.ts

@@ -802,4 +802,18 @@ export const STANDARD_COMMAND_MENU_ITEMS = {
     engineComponentKey: EngineComponentKey.REPLY_TO_EMAIL_THREAD,
     hotKeys: null,
   },
+  composeEmail: {
+    universalIdentifier: '96457c5a-b028-4d48-94e3-27f4c41296b8',
+    label: 'Compose Email',
+    icon: 'IconMail',
+    isPinned: false,
+    position: 71,
+    shortLabel: 'Compose',
+    availabilityType: CommandMenuItemAvailabilityType.GLOBAL,
+    conditionalAvailabilityExpression: null,
+    availabilityObjectMetadataUniversalIdentifier: null,
+    frontComponentUniversalIdentifier: null,
+    engineComponentKey: EngineComponentKey.COMPOSE_EMAIL,
+    hotKeys: null,
+  },
 } as const;