fix: Change messages.source_id to text column (#12908)

## Summary
Changes `messages.source_id` from `string` (255 char limit) to `text`
(20,000 char limit) to support long email Message-ID headers.

## Changes
- Migration to change column type from string to text
- Added spec tests for source_id length validation

## Related
Fixes
https://linear.app/chatwoot/issue/CW-5961/activerecordrecordinvalid-validation-failed-source-is-too-long-maximum

app/models/message.rb

@@ -20,7 +20,7 @@
 #  conversation_id           :integer          not null
 #  inbox_id                  :integer          not null
 #  sender_id                 :bigint
-#  source_id                 :string
+#  source_id                 :text
 #
 # Indexes
 #

db/migrate/20251119161025_change_messages_source_id_to_text.rb

@@ -0,0 +1,9 @@
+class ChangeMessagesSourceIdToText < ActiveRecord::Migration[7.1]
+  def up
+    change_column :messages, :source_id, :text
+  end
+
+  def down
+    change_column :messages, :source_id, :string
+  end
+end

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.1].define(version: 2025_11_14_173609) do
+ActiveRecord::Schema[7.1].define(version: 2025_11_19_161025) do
   # These extensions should be enabled to support this database
   enable_extension "pg_stat_statements"
   enable_extension "pg_trgm"
@@ -954,7 +954,7 @@ ActiveRecord::Schema[7.1].define(version: 2025_11_14_173609) do
     t.datetime "updated_at", precision: nil, null: false
     t.boolean "private", default: false, null: false
     t.integer "status", default: 0
-    t.string "source_id"
+    t.text "source_id"
     t.integer "content_type", default: 0, null: false
     t.json "content_attributes", default: {}
     t.string "sender_type"

spec/models/message_spec.rb

@@ -45,6 +45,48 @@ RSpec.describe Message do
         end
       end
     end
+
+    context 'when it validates source_id length' do
+      it 'valid when source_id is within text limit (20000 chars)' do
+        long_source_id = 'a' * 10_000
+        message.source_id = long_source_id
+        expect(message.valid?).to be true
+      end
+
+      it 'valid when source_id is exactly 20000 characters' do
+        long_source_id = 'a' * 20_000
+        message.source_id = long_source_id
+        expect(message.valid?).to be true
+      end
+
+      it 'invalid when source_id exceeds text limit (20000 chars)' do
+        long_source_id = 'a' * 20_001
+        message.source_id = long_source_id
+        message.valid?
+
+        expect(message.errors[:source_id]).to include('is too long (maximum is 20000 characters)')
+      end
+
+      it 'handles long email Message-ID headers correctly' do
+        # Simulate a long Message-ID like some email systems generate
+        long_message_id = "msg-#{SecureRandom.hex(240)}@verylongdomainname.example.com"[0...500]
+        message.source_id = long_message_id
+        message.content_type = 'incoming_email'
+
+        expect(message.valid?).to be true
+        expect(message.source_id.length).to eq(500)
+      end
+
+      it 'allows nil source_id' do
+        message.source_id = nil
+        expect(message.valid?).to be true
+      end
+
+      it 'allows empty string source_id' do
+        message.source_id = ''
+        expect(message.valid?).to be true
+      end
+    end
   end
 
   describe 'concerns' do