Add manager controller for bill signatures

app/dashboards/bill_signature_dashboard.rb

@@ -0,0 +1,22 @@
+require "administrate/base_dashboard"
+
+class BillSignatureDashboard < Administrate::BaseDashboard
+  ATTRIBUTE_TYPES = {
+    dossier_operation_logs: Field::HasMany,
+    id: Field::Number,
+    digest: Field::String,
+    created_at: Field::DateTime,
+    updated_at: Field::DateTime,
+    serialized: AttachmentField,
+    signature: AttachmentField
+  }.freeze
+
+  COLLECTION_ATTRIBUTES = [
+    :id,
+    :created_at,
+    :dossier_operation_logs,
+    :digest,
+    :serialized,
+    :signature
+  ].freeze
+end