chore: Add documentation for API channel (#1179)

docs/channels/api-channel/callback-url.md

@@ -0,0 +1,45 @@
+---
+path: '/docs/channels/api/callback-url'
+title: 'Callback URL and message payload'
+---
+
+When a new message is created in the API channel, you will get a POST request to the Callback URL specified while creating the API channel. The payload would look like this.
+
+**Event type**: `message_created`
+
+```json
+{
+  "id": 0,
+  "content": "This is a incoming message from API Channel",
+  "created_at": "2020-08-30T15:43:04.000Z",
+  "message_type": "incoming",
+  "content_type": null,
+  "content_attributes": {},
+  "source_id": null,
+  "sender": {
+    "id": 0,
+    "name": "contact-name",
+    "avatar": "",
+    "type": "contact"
+  },
+  "inbox": {
+    "id": 0,
+    "name": "API Channel"
+  },
+  "conversation": {
+    "additional_attributes": null,
+    "channel": "Channel::Api",
+    "id": 0,
+    "inbox_id": 0,
+    "status": "open",
+    "agent_last_seen_at": 0,
+    "user_last_seen_at": 0,
+    "timestamp": 0
+  },
+  "account": {
+    "id": 1,
+    "name": "API testing"
+  },
+  "event": "message_created"
+}
+```

docs/channels/api-channel/create-channel.md

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+---
+path: '/docs/channels/api/configure'
+title: 'How to create an API channel inbox?'
+---
+
+Setting up an API channel consists of the following steps.
+
+1. Create API Channel inbox
+2. Send messages using Chatwoot APIs
+3. Receive webhooks on new messages from Chatwoot
+
+This document allows you to create and configure an API channel inbox in Chatwoot installations.
+
+**Step 1**: Go to Settings > Inboxes and click on "Add Inbox".
+
+**Step 2**: Select **API** from the list of channels.
+
+![select-api-inbox](./images/select-api-inbox.png)
+
+**Step 3**: Provide an name for the channel and a callback URL (the events and corresponding payload is defined in the subsequent articles)
+
+![configure-screen](./images/configure-screen.png)
+
+**Step 4**: Add agents to the inbox.
+
+![add-agents](./images/add-agents.png)
+
+**Step 5**: Hooray!! The inbox setup is complete.
+
+![take-me-there](./images/take-me-there.png)
+
+![inbox-welcome-screen](./images/inbox-welcome-screen.png)
+
+Now the channel setup is complete, let us try to send a message using Chatwoot APIs. Read more about it [here](/docs/channels/api/send-messages)

docs/channels/api-channel/send-message-api-channel.md

@@ -0,0 +1,113 @@
+---
+path: '/docs/channels/api/send-messages'
+title: 'Send messages to API channel'
+---
+
+To send messages to API channel, you need have a basic understanding of the models and nomenclature used in Chatwoot. Let us try to understand these first.
+
+1. **Channel**: Channel defines the type of the source of conversations. Eg: Facebook, Twitter, API etc.
+
+2. **Inbox**: You can create multiple sources of conversations which is of the same channel type. For eg: You can have more than one Facebook page connected to a Chatwoot account. Each page is called as the inbox in Chatwoot.
+
+3. **Conversation**: A Conversation is a collection of messages.
+
+4. **Contact**: Each conversation has a real life person associated with it, this person is called a contact.
+
+5. **Contact Inboxes**: This is the session for each contact on a inbox. A contact can have multiple sessions and multiple conversations in the same inbox.
+
+### How to send a message in an API Channel?
+
+To send a message in an API channel, you have to create a contact, then create a conversation and then send a message.
+
+APIs require `api_access_token` in the request header. You can get this token by visiting your Profile settings >  Access Token
+
+#### 1. Create a contact
+
+API documentation: (https://www.chatwoot.com/developers/api/#operation/contactCreate)
+
+Pass the inbox id of the API channel along with other params specified. This would create a session for you automatically. A sample response would look like the one below.
+
+```json
+{
+  "email": "string",
+  "name": "string",
+  "phone_number": "string",
+  "thumbnail": "string",
+  "additional_attributes": {},
+  "contact_inboxes": [
+    {
+      "source_id": "string",
+      "inbox": {
+        "id": 0,
+        "name": "string",
+        "website_url": "string",
+        "channel_type": "string",
+        "avatar_url": "string",
+        "widget_color": "string",
+        "website_token": "string",
+        "enable_auto_assignment": true,
+        "web_widget_script": "string",
+        "welcome_title": "string",
+        "welcome_tagline": "string",
+        "greeting_enabled": true,
+        "greeting_message": "string"
+      }
+    }
+  ],
+  "id": 0,
+  "availability_status": "string"
+}
+```
+
+As you can see in the payload, you will be able to see the `contact_inboxes` and each `contact_inbox` will have a `source_id`. Source Id can be seen as the session identifier. You will use this source_id to create a new conversation as defined below.
+
+#### 2. Create a conversation
+
+API documentation: (https://www.chatwoot.com/developers/api/#operation/newConversation)
+
+Use the `source_id` received in the previous API call.
+
+You will receive a conversation id which can be used to create a message.
+
+```json
+{
+  "id": 0
+}
+```
+
+#### 3. Create a new message
+
+API documentation: (https://www.chatwoot.com/developers/api/#operation/conversationNewMessage)
+
+There are 2 types of messages.
+
+1. **Incoming**: Messages sent by the end user is classified as an incoming message.
+
+2. **Outgoing**: Messages sent by the agent is classified as an outgoing message.
+
+If you call the API with the correct content, you will receive a payload similar to the one below.
+
+```json
+{
+    "id": 0,
+    "content": "This is a incoming message from API Channel",
+    "inbox_id": 0,
+    "conversation_id": 0,
+    "message_type": 0,
+    "content_type": null,
+    "content_attributes": {},
+    "created_at": 0,
+    "private": false,
+    "sender": {
+        "id": 0,
+        "name": "Pranav",
+        "type": "contact"
+    }
+}
+```
+
+If everything is sucessful you will see the conversation on the dashboard as follows.
+
+![conversation](./images/conversation.png)
+
+You will be notified when a new message is created on the URL specified while creating the API channel. You can read about the message payload [here](/docs/channels/api/callback-url)