Chore: Scope URLs with account_id (#601)

* Chore: Enable Users to create multiple accounts

Addresses: #402
- migrations to split roles and other attributes from users table
- make changes in code to accommodate this change

Co-authored-by: Pranav Raj Sreepuram <pranavrajs@gmail.com>

app/controllers/api/v1/accounts/conversations/assignments_controller.rb

@@ -0,0 +1,11 @@
+class Api::V1::Accounts::Conversations::AssignmentsController < Api::BaseController
+  before_action :set_conversation, only: [:create]
+
+  # assign agent to a conversation
+  def create
+    # if params[:assignee_id] is not a valid id, it will set to nil, hence unassigning the conversation
+    assignee = current_account.users.find_by(id: params[:assignee_id])
+    @conversation.update_assignee(assignee)
+    render json: assignee
+  end
+end