Unnecessary call to Utilities.formatString

[tdelmas]

https://github.com/gsuitedevs/apps-script-oauth2/blob/master/src/OAuth2.js#L67

return Utilities.formatString('https://script.google.com/macros/d/%s/usercallback', scriptId);

I think that calls to Utilities.formatString should simply be replaced by:

return 'https://script.google.com/macros/d/'+scriptId+'/usercallback';

Or, if we want to be really conservative:

return 'https://script.google.com/macros/d/'+encodeURIComponent(scriptId)+'/usercallback';

[erickoledadevrel]

I prefer the readability of formatString, but worth optimizing for performance. Done!

[tdelmas]

I like that readability too, but as the string is not configurable, I prefer the performance. Thanks!