show accounts for current user on /accounts endpoint

app/controllers/api/accounts_controller.rb

@@ -0,0 +1,5 @@
+class Api::AccountsController < Api::ApiController
+  def show
+    render jsonapi: current_user.accounts
+  end
+end

app/serializers/serializable_account.rb

@@ -0,0 +1,21 @@
+class SerializableAccount < JSONAPI::Serializable::Resource
+  type "account"
+
+  attributes :name
+
+  attribute :users do
+    @object.users.map do |user|
+      if user.avatar.attached?
+        avatar = Rails.application.routes.url_helpers.rails_blob_url(user.avatar, host: AppHost.new.domain_with_port)
+      else
+        avatar = nil
+      end
+      {
+        email: user.email,
+        name: user.full_name,
+        role: user.account_auths.map(&:role).compact.join(", "),
+        avatar: avatar
+      }
+    end
+  end
+end