ActivePieces (activepieces.com) is an authentication service which is easier to use than n8n and cheaper than Zapier (1000 free tasks per month then $1 per 1000 additional tasks).
There is no current Integration with Grist, however it has been requested by two separate Grist users
ActivePieces invite developers to contribute pieces to integrate with other platforms which they describe here: Overview - Activepieces
I am not a developer and have no idea the size of this task, but I am wondering if anyone would like to take on this project?
As an incentive, contributing a piece receives a reward of 1,400 free tasks per month which amounts to about $16.80 per year 
Anyone interested?
