allow hash interpolation in database configs

test plan:
 * set something like username: canvas
   schema_search_path: "%{username},public" in database.yml
 * it should work

Change-Id: I904f83c2ebeea0139e80ac1566a7e934ba3c1eef
Reviewed-on: https://gerrit.instructure.com/13806
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jacob Fugal <jacob@instructure.com>

config/initializers/connection_specification.rb

@@ -13,7 +13,13 @@ ActiveRecord::Base::ConnectionSpecification.class_eval do
     if self.class.environment && @config.has_key?(self.class.environment)
       @current_config.merge!(@config[self.class.environment].symbolize_keys)
     end
+
+    @current_config.keys.each do |key|
+      next unless @current_config[key].is_a?(String)
+      @current_config[key] = I18n.interpolate_hash(@current_config[key], @current_config)
+    end
     @current_config[:username] = @current_config[:username].gsub('{schema}', @current_config[:schema_search_path]) if @current_config[:username] && @current_config[:schema_search_path]
+
     if self.class.explicit_user
       @current_config[:username] = self.class.explicit_user
       @current_config.delete(:password)

spec/lib/connection_specification_with_environment_spec.rb

@@ -48,11 +48,11 @@ describe ActiveRecord::Base::ConnectionSpecification do
     spec.config[:database].should == 'master'
   end
 
-  it "should allow using {schema} as an insertion into the username" do
+  it "should allow using hash insertions" do
     conf = {
         :adapter => 'postgresql',
         :database => 'master',
-        :username => '{schema}',
+        :username => '%{schema_search_path}',
         :schema_search_path => 'canvas',
         :deploy => {
             :username => 'deploy'
@@ -70,7 +70,7 @@ describe ActiveRecord::Base::ConnectionSpecification do
     conf = {
         :adapter => 'postgresql',
         :database => 'master',
-        :username => '{schema}',
+        :username => '%{schema_search_path}',
         :schema_search_path => 'canvas',
         :deploy => {
             :username => 'deploy'