src/ln: change formatter argument to a table with formatter

spec/ln_spec.lua

@@ -59,4 +59,14 @@ describe("ln", function()
       assert.truthy(string.find(msg, 'foo="bar with spaces"'))
     end)
   end)
+           
+  describe("logger options", function()
+    local lgr = ln.Logger:new {
+      formatter = ln.LogfmtFormatter:new()
+    }
+    
+    it("sets the formatter to non-nil", function()
+      assert.truthy(lgr.formatter)
+    end)
+  end)
 end)

src/ln.lua

@@ -68,13 +68,12 @@ function Logger:log(...)
   print(message)
 end
 
-function Logger:new(formatter)
+function Logger:new(o)
-  if formatter == nil then
+  if o == nil then
+    o = {
       formatter = LogfmtFormatter:new()
-  end
-  local o = {
-    formatter = formatter,
     }
+  end
   setmetatable(o, self)
   self.__index = self
   return o