Reduce path to 512 chars to make id+path index to work with mysql

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

db/schema.rb

@@ -1928,7 +1928,7 @@ ActiveRecord::Schema.define(version: 20180810155213) do
     t.string "app_group", null: false
     t.string "app_name", null: false
     t.string "app_version"
-    t.string "path", limit: 1024, null: false
+    t.string "path", limit: 512, null: false
   end
 
   add_index "packages_maven_metadata", ["package_id", "path"], name: "index_packages_maven_metadata_on_package_id_and_path", using: :btree

ee/db/migrate/20180720121404_create_packages_maven_metadata.rb

@@ -15,7 +15,7 @@ class CreatePackagesMavenMetadata < ActiveRecord::Migration
       t.string :app_group, null: false
       t.string :app_name, null: false
       t.string :app_version
-      t.string :path, limit: 1024, null: false
+      t.string :path, limit: 512, null: false
     end
 
     add_concurrent_foreign_key :packages_maven_metadata, :packages_packages,