Reliably parse query params from connection string (#485)

The previous regex used the match query options was incorrect since it only
captured words (`\w+`) values from query params. This would cause params with
values such as `&host=/path/to/my/socket` to be parsed as `nil`, which is
incorrect and will cause pain on some hosting providers (i.e. Google Cloud
requires a path to a socket).

Parsing query params can be brittle, so we opt to let `CGI.parse` to do the
heavy lifting since it is more battle-tested.

lib/hanami/model/migrator/connection.rb

@@ -1,3 +1,5 @@
+require 'cgi'
+
 module Hanami
   module Model
     class Migrator
@@ -153,8 +155,11 @@ def table(name)
         #
         # @since 0.5.0
         # @api private
-        def parsed_opt(option)
-          parsed_uri.to_s.match(/[\?|\&]#{ option }=(\w+)\&?/).to_a.last
+        def parsed_opt(option, query: parsed_uri.query)
+          return if query.nil?
+
+          @parsed_query_opts ||= CGI.parse(query)
+          @parsed_query_opts[option].to_a.last
         end
       end
     end

spec/unit/hanami/model/migrator/connection_spec.rb

@@ -26,8 +26,36 @@
     end
 
     describe '#host' do
-      it 'returns configured host' do
-        expect(connection.host).to eq('127.0.0.1')
+      describe 'when the host is only specified in the URI' do
+        let(:url) { "postgresql://127.0.0.1/database" }
+
+        it 'returns configured host' do
+          expect(connection.host).to eq('127.0.0.1')
+        end
+      end
+
+      describe 'when the host is only specified in the query' do
+        let(:url) { "postgresql:///database?host=0.0.0.0" }
+
+        it 'returns the host specified in the query param' do
+          expect(connection.host).to eql('0.0.0.0')
+        end
+      end
+
+      describe 'when the host is specified as a socket' do
+        let(:url) { "postgresql:///database?host=/path/to/my/sock" }
+
+        it 'returns the path to the socket specified in the query param' do
+          expect(connection.host).to eql('/path/to/my/sock')
+        end
+      end
+
+      describe 'when the host is specified in both the URI and query' do
+        let(:url) { "postgresql://127.0.0.1/database?host=0.0.0.0" }
+
+        it 'prefers the host from the URI' do
+          expect(connection.host).to eql('127.0.0.1')
+        end
       end
     end