API improvements and bug fixes

new Added a new endpoint to change the campaign of a promoter. You can find more details here.

improvement you can now find promoters in Promoters API endpoints by email as well, using "promoter_email" parameter.

improvement added "currency" parameter in track/sale API endpoint so you can send amounts in different currencies. We'll convert it using daily updated FX rates to the default currency set in your FirstPromoter Settings.

improvement promoters/list API endpoint is much faster now

fix sales could be added manually even though they didn't generate commissions when a wrong plan id was used

fix some number formatting issue in promoters' Details section

fix {{lead.email}} tag didn't work on commission earned emails