Drop types_de_piece_justificative and pieces_justificatives tables

Now that the content of these tables has been migrated, we can drop
them.

db/migrate/20190730153555_drop_deprecated_piece_justificative_tables.rb

@@ -0,0 +1,40 @@
+class DropDeprecatedPieceJustificativeTables < ActiveRecord::Migration[5.2]
+  def change
+    assert_empty_table!(:types_de_piece_justificative)
+    assert_empty_table!(:pieces_justificatives)
+
+    drop_table :types_de_piece_justificative do |t|
+      t.string "libelle"
+      t.string "description"
+      t.boolean "api_entreprise", default: false
+      t.datetime "created_at", null: false
+      t.datetime "updated_at", null: false
+      t.integer "procedure_id"
+      t.integer "order_place"
+      t.string "lien_demarche"
+      t.boolean "mandatory", default: false
+      t.index ["procedure_id"], name: "index_types_de_piece_justificative_on_procedure_id"
+    end
+
+    drop_table :pieces_justificatives do |t|
+      t.string "content"
+      t.integer "dossier_id"
+      t.integer "type_de_piece_justificative_id"
+      t.datetime "created_at"
+      t.integer "user_id"
+      t.string "original_filename"
+      t.string "content_secure_token"
+      t.datetime "updated_at"
+      t.index ["dossier_id"], name: "index_pieces_justificatives_on_dossier_id"
+      t.index ["type_de_piece_justificative_id"], name: "index_pieces_justificatives_on_type_de_piece_justificative_id"
+    end
+  end
+
+  def assert_empty_table!(table)
+    results = ActiveRecord::Base.connection.exec_query("SELECT COUNT(*) FROM #{table}")
+    records_count = results.first['count']
+    if records_count > 0
+      raise "Abord dropping `#{table}` table: it still contains #{records_count} records."
+    end
+  end
+end