⚡ Introduce a new high-performing standalone chat API (#1200)

Closes #1154

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

- **New Features**
	- Added authentication functionality for user sessions in chat API.
- Introduced chat-related API endpoints for starting, previewing, and
continuing chat sessions, and streaming messages.
- Implemented WhatsApp API webhook handling for receiving and processing
messages.
- Added environment variable `NEXT_PUBLIC_CHAT_API_URL` for chat API URL
configuration.

- **Bug Fixes**
	- Adjusted file upload logic to correctly determine the API host.
	- Fixed message streaming URL in chat integration with OpenAI.

- **Documentation**
- Updated guides for creating blocks, local installation, self-hosting,
and deployment to use `bun` instead of `pnpm`.

- **Refactor**
	- Refactored chat API functionalities to use modular architecture.
- Simplified client log saving and session update functionalities by
using external functions.
	- Transitioned package management and workflow commands to use `bun`.

- **Chores**
- Switched to `bun` for package management in Dockerfiles and GitHub
workflows.
	- Added new Dockerfile for chat API service setup with Bun framework.
	- Updated `.prettierignore` and documentation with new commands.

- **Style**
	- No visible changes to end-users.

- **Tests**
	- No visible changes to end-users.

- **Revert**
	- No reverts in this release.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/bot-engine/apiHandlers/startChat.ts

@@ -0,0 +1,107 @@
+import { computeCurrentProgress } from '../computeCurrentProgress'
+import { filterPotentiallySensitiveLogs } from '../logs/filterPotentiallySensitiveLogs'
+import { restartSession } from '../queries/restartSession'
+import { saveStateToDatabase } from '../saveStateToDatabase'
+import { startSession } from '../startSession'
+
+type Props = {
+  origin: string | undefined
+  message?: string
+  isOnlyRegistering: boolean
+  publicId: string
+  isStreamEnabled: boolean
+  prefilledVariables?: Record<string, unknown>
+  resultId?: string
+}
+
+export const startChat = async ({
+  origin,
+  message,
+  isOnlyRegistering,
+  publicId,
+  isStreamEnabled,
+  prefilledVariables,
+  resultId: startResultId,
+}: Props) => {
+  const {
+    typebot,
+    messages,
+    input,
+    resultId,
+    dynamicTheme,
+    logs,
+    clientSideActions,
+    newSessionState,
+    visitedEdges,
+  } = await startSession({
+    version: 2,
+    startParams: {
+      type: 'live',
+      isOnlyRegistering,
+      isStreamEnabled,
+      publicId,
+      prefilledVariables,
+      resultId: startResultId,
+    },
+    message,
+  })
+
+  let corsOrigin
+
+  if (
+    newSessionState.allowedOrigins &&
+    newSessionState.allowedOrigins.length > 0
+  ) {
+    if (origin && newSessionState.allowedOrigins.includes(origin))
+      corsOrigin = origin
+    else corsOrigin = newSessionState.allowedOrigins[0]
+  }
+
+  const session = isOnlyRegistering
+    ? await restartSession({
+        state: newSessionState,
+      })
+    : await saveStateToDatabase({
+        session: {
+          state: newSessionState,
+        },
+        input,
+        logs,
+        clientSideActions,
+        visitedEdges,
+        hasCustomEmbedBubble: messages.some(
+          (message) => message.type === 'custom-embed'
+        ),
+      })
+
+  const isEnded =
+    newSessionState.progressMetadata &&
+    !input?.id &&
+    (clientSideActions?.filter((c) => c.expectsDedicatedReply).length ?? 0) ===
+      0
+
+  return {
+    sessionId: session.id,
+    typebot: {
+      id: typebot.id,
+      theme: typebot.theme,
+      settings: typebot.settings,
+    },
+    messages,
+    input,
+    resultId,
+    dynamicTheme,
+    logs: logs?.filter(filterPotentiallySensitiveLogs),
+    clientSideActions,
+    corsOrigin,
+    progress: newSessionState.progressMetadata
+      ? isEnded
+        ? 100
+        : computeCurrentProgress({
+            typebotsQueue: newSessionState.typebotsQueue,
+            progressMetadata: newSessionState.progressMetadata,
+            currentInputBlockId: input?.id,
+          })
+      : undefined,
+  }
+}