⚡ (setVariable) Add "Environment name" value in Set variable block (#850)

Closes #848
<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
### Summary by CodeRabbit

- New Feature: Added "Environment name" as a new value type in the
SetVariable function, allowing users to distinguish between 'web' and
'whatsapp' environments.
- Refactor: Simplified session state handling in `resumeWhatsAppFlow.ts`
for improved code clarity.
- Refactor: Updated `startWhatsAppSession.ts` to include an initial
session state with WhatsApp contact and expiry timeout, enhancing
session management.
- Bug Fix: Improved null handling in `executeSetVariable.ts` for
'Contact name' and 'Phone number', preventing potential issues with
falsy values.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/bot-engine/startSession.ts

@@ -30,11 +30,13 @@ import { injectVariablesFromExistingResult } from './variables/injectVariablesFr
 type Props = {
   startParams: StartParams
   userId: string | undefined
+  initialSessionState?: Pick<SessionState, 'whatsApp' | 'expiryTimeout'>
 }
 
 export const startSession = async ({
   startParams,
   userId,
+  initialSessionState,
 }: Props): Promise<ChatReply & { newSessionState: SessionState }> => {
   if (!startParams)
     throw new TRPCError({
@@ -108,6 +110,7 @@ export const startSession = async ({
     dynamicTheme: parseDynamicThemeInState(typebot.theme),
     isStreamEnabled: startParams.isStreamEnabled,
     typingEmulation: typebot.settings.typingEmulation,
+    ...initialSessionState,
   }
 
   if (startParams.isOnlyRegistering) {