Generate models necessary for maven repository backend

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

app/models/packages.rb

+module Packages
+  def self.table_name_prefix
+    'packages_'
+  end
+end

app/models/packages/maven_metadatum.rb

+class Packages::MavenMetadatum < ActiveRecord::Base
+  belongs_to :package
+end

app/models/packages/package.rb

+class Packages::Package < ActiveRecord::Base
+  belongs_to :project
+end

app/models/packages/package_file.rb

+class Packages::PackageFile < ActiveRecord::Base
+  belongs_to :package
+end

db/migrate/20180720120026_create_packages_package_files.rb

+class CreatePackagesPackageFiles < ActiveRecord::Migration
+  DOWNTIME = false
+
+  def change
+    create_table :packages_package_files do |t|
+      t.references :package, index: true, foreign_key: true, null: false
+      t.string :file
+      t.integer :file_type
+      t.integer :size
+      t.binary :file_md5
+      t.binary :file_sha1
+
+      t.timestamps null: false
+    end
+  end
+end

db/migrate/20180720120716_create_packages_packages.rb

+class CreatePackagesPackages < ActiveRecord::Migration
+  def change
+    create_table :packages_packages do |t|
+      t.references :project, index: true, foreign_key: true, null: false
+      t.string :name
+      t.string :version
+
+      t.timestamps null: false
+    end
+  end
+end

db/migrate/20180720121404_create_packages_maven_metadata.rb

+class CreatePackagesMavenMetadata < ActiveRecord::Migration
+  def change
+    create_table :packages_maven_metadata do |t|
+      t.references :package, index: true, foreign_key: true, null: false
+      t.string :app_group, null: false
+      t.string :app_name, null: false
+      t.string :app_version, null: false
+
+      t.timestamps null: false
+    end
+  end
+end

spec/models/packages/maven_metadatum_spec.rb

+require 'rails_helper'
+
+RSpec.describe Packages::MavenMetadatum, type: :model do
+  pending "add some examples to (or delete) #{__FILE__}"
+end

spec/models/packages/package_file_spec.rb

+require 'rails_helper'
+
+RSpec.describe Packages::PackageFile, type: :model do
+  pending "add some examples to (or delete) #{__FILE__}"
+end

spec/models/packages/package_spec.rb

+require 'rails_helper'
+
+RSpec.describe Packages::Package, type: :model do
+  pending "add some examples to (or delete) #{__FILE__}"
+end