DEV: adds blocks support to chat messages (#29782)

Blocks allow BOTS to augment the capacities of a chat message. At the moment only one block is available: `actions`, accepting only one type of element: `button`.

<img width="708" alt="Screenshot 2024-11-15 at 19 14 02" src="https://github.com/user-attachments/assets/63f32a29-05b1-4f32-9edd-8d8e1007d705">

# Usage

```ruby
Chat::CreateMessage.call(
  params: {
    message: "Welcome!",
    chat_channel_id: 2,
    blocks: [
      {
         type: "actions",
         elements: [
           { value: "foo", type: "button", text: { text: "How can I install themes?", type: "plain_text" } }
         ]
      }
    ]
  },
  guardian: Discourse.system_user.guardian
)
```

# Documentation

## Blocks

### Actions

Holds interactive elements: button.

#### Fields

| Field | Type | Description | Required? |
|--------|--------|--------|--------|
| type | string | For an actions block, type is always `actions` | Yes |
| elements | array | An array of interactive elements, maximum 10 elements | Yes |
| block_id | string | An unique identifier for the block, will be generated if not specified. It has to be unique per message | No |

#### Example

```json
{
  "type": "actions",
  "block_id": "actions_1",
  "elements": [...]
}
```

## Elements

### Button

#### Fields

| Field | Type | Description | Required? |
|--------|--------|--------|--------|
| type | string | For a button, type is always `button` | Yes |
| text | object | A text object holding the type and text. Max 75 characters | Yes |
| value | string | The value returned after the interaction has been validated. Maximum length is 2000 characters | No |
| style | string | Can be `primary` ,  `success` or `danger` | No |
| action_id | string | An unique identifier for the action, will be generated if not specified. It has to be unique per message | No |

#### Example

```json
{
  "type": "actions",
  "block_id": "actions_1",
  "elements": [
    {
      "type": "button",
      "text": {
          "type": "plain_text",
          "text": "Ok"
      },
      "value": "ok",
      "action_id": "button_1"
    }
  ]
}
```

## Interactions

When a user interactions with a button the following flow will happen:

- We send an interaction request to the server
- Server checks if the user can make this interaction
- If the user can make this interaction, the server will:

  * `DiscourseEvent.trigger(:chat_message_interaction, interaction)`
  * return a JSON document
  
  ```json
  {
    "interaction": {
        "user": {
            "id": 1,
            "username": "j.jaffeux"
        },
        "channel": {
            "id": 1,
            "title": "Staff"
        },
        "message": {
            "id": 1,
            "text": "test",
            "user_id": -1
        },
        "action": {
            "text": {
                "text": "How to install themes?",
                "type": "plain_text"
            },
            "type": "button",
            "value": "click_me_123",
            "action_id": "bf4f30b9-de99-4959-b3f5-632a6a1add04"
        }
    }
  }
  ```
  * Fire a `appEvents.trigger("chat:message_interaction", interaction)`

plugins/chat/app/models/chat/message.rb

@@ -19,6 +19,10 @@ module Chat
     belongs_to :last_editor, class_name: "User"
     belongs_to :thread, class_name: "Chat::Thread", optional: true, autosave: true
 
+    has_many :interactions,
+             class_name: "Chat::MessageInteraction",
+             dependent: :destroy,
+             foreign_key: :chat_message_id
     has_many :replies,
              class_name: "Chat::Message",
              foreign_key: "in_reply_to_id",
@@ -91,11 +95,28 @@ module Chat
 
     before_save { ensure_last_editor_id }
 
-    validates :cooked, length: { maximum: 20_000 }
-    validate :validate_message
+    normalizes :blocks,
+               with: ->(blocks) do
+                 return if !blocks
+
+                 # automatically assigns unique IDs
+                 blocks.each do |block|
+                   block["schema_version"] = 1
+                   block["block_id"] ||= SecureRandom.uuid
+                   block["elements"].each do |element|
+                     element["schema_version"] = 1
+                     element["action_id"] ||= SecureRandom.uuid if element["type"] == "button"
+                   end
+                 end
+               end
 
     def self.polymorphic_class_mapping = { "ChatMessage" => Chat::Message }
 
+    validates :cooked, length: { maximum: 20_000 }
+
+    validates_with Chat::MessageBlocksValidator
+
+    validate :validate_message
     def validate_message
       WatchedWordsValidator.new(attributes: [:message]).validate(self)
 

plugins/chat/app/models/chat/message_interaction.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+module Chat
+  class MessageInteraction < ActiveRecord::Base
+    self.table_name = "chat_message_interactions"
+
+    belongs_to :user
+    belongs_to :message, class_name: "Chat::Message", foreign_key: "chat_message_id"
+  end
+end
+
+# == Schema Information
+#
+# Table name: chat_message_interactions
+#
+#  id              :bigint           not null, primary key
+#  user_id         :bigint           not null
+#  chat_message_id :bigint           not null
+#  action          :jsonb            not null
+#  created_at      :datetime         not null
+#  updated_at      :datetime         not null
+#
+# Indexes
+#
+#  index_chat_message_interactions_on_chat_message_id  (chat_message_id)
+#  index_chat_message_interactions_on_user_id          (user_id)
+#