Server which processes older actions, which might be unprocessed because of not queue was available, or processing failed.

We process the actions one by one synchronously because the processing will update the associated supporter.

We use thre intervals to control processing of old actions:

• @time_margin - (1 minute default) - do not process actions more recent then one minute - they might be actually still processed by async-after-add processing.

• interval (given as argument to ProcessOld.start_link, 30 sec default) - how often should we check for old actions

• @batch_interval (1 second default) - how long to wait between processing of 1000 actions batch.