Improvements in batchsize for log cleaning, index on created_at, avoiding extra db update call.

[igorwulff]

• created_at index created since it is called for log cleaning and can take long depending on the log table size.
• Added a default batch_size that is a bit saner then 2.
• Avoiding an extra database update call in the before plugin.

[thomas-kl1]

@daniloargentiero @ugoliniriccardo please merge this :D

[ssx]

@thomas-kl1 @igorwulff I've forked this and will add these changes later today: https://github.com/ssx/module-webapi-logs

[ssx]

@ugoliniriccardo I've got a few more features I'm about to write too. Will PR once done.