feat: wrap join alias in quotes

BREAKING CHANGE: this allows to avoid keywords being used as aliases (e.g. "user")

Author: vladfaust

spec/query/join_spec.cr

@@ -19,7 +19,7 @@ describe "Atom::Query#join" do
         q = Atom::Query(User).new.join(:authored_posts)
 
         q.to_s.should eq <<-SQL
-        SELECT users.* FROM users INNER JOIN posts AS authored_posts ON authored_posts.author_uuid = users.uuid
+        SELECT users.* FROM users INNER JOIN posts AS "authored_posts" ON "authored_posts".author_uuid = users.uuid
         SQL
 
         q.params.should be_nil
@@ -31,7 +31,7 @@ describe "Atom::Query#join" do
         q = Atom::Query(User).new.join(:authored_posts, type: :right, as: "the_posts", select: {"created_at", "id"})
 
         q.to_s.should eq <<-SQL
-        SELECT users.*, '' AS _authored_posts, the_posts.created_at, the_posts.id FROM users RIGHT JOIN posts AS the_posts ON the_posts.author_uuid = users.uuid
+        SELECT users.*, '' AS _authored_posts, "the_posts".created_at, "the_posts".id FROM users RIGHT JOIN posts AS "the_posts" ON "the_posts".author_uuid = users.uuid
         SQL
 
         q.params.should be_nil
@@ -44,7 +44,7 @@ describe "Atom::Query#join" do
       q = Atom::Query(Post).new.join(:author, type: :left, select: "id")
 
       q.to_s.should eq <<-SQL
-      SELECT posts.*, '' AS _author, author.id FROM posts LEFT JOIN users AS author ON posts.author_uuid = author.uuid
+      SELECT posts.*, '' AS _author, "author".id FROM posts LEFT JOIN users AS "author" ON posts.author_uuid = "author".uuid
       SQL
 
       q.params.should be_nil

src/atom/query/join.cr

@@ -101,9 +101,9 @@ class Atom
       select _select : Char | String | Enumerable(String | Char) | Nil = nil
     )
       on = if reference.direct?
-             "#{T.table}.#{reference.key} = #{_as}.#{reference.primary_key}"
+             "#{T.table}.#{reference.key} = \"#{_as}\".#{reference.primary_key}"
            else
-             "#{_as}.#{reference.foreign_key} = #{T.table}.#{T.primary_key.key}"
+             "\"#{_as}\".#{reference.foreign_key} = #{T.table}.#{T.primary_key.key}"
            end
 
       if _select
@@ -115,10 +115,10 @@ class Atom
 
         if _select.is_a?(Enumerable)
           _select.each do |s|
-            self.select(_as ? _as + '.' + s : s)
+            self.select(_as ? "\"#{_as}\"" + '.' + s : s)
           end
         else
-          self.select(_as ? _as + '.' + _select : _select)
+          self.select(_as ? "\"#{_as}\"" + '.' + _select : _select)
         end
       end
 
@@ -141,7 +141,7 @@ class Atom
       unless @join.nil?
         {{query}} += @join.not_nil!.join(" ") do |join|
           j = " #{join.type} JOIN #{join.table}"
-          j += (" AS #{join.alias}") if join.alias && join.table != join.alias
+          j += (" AS \"#{join.alias}\"") if join.alias && join.table != join.alias
           j += " ON #{join.on}"
         end
       end