Update GetResponse API Calls to v3 of the API

[patdumond]

s2Member is currently using v2 of the GetResponse API. v2 isn't actually even supported by GetResponse anymore: they support v1.5 and v3. The API calls from s2Member are being handled by the legacy v1.5 API at GetResponse. Most things work fine, but there are issues with some Workflow Automation triggers that GetResponse support says only work with v3 of the API.

I took a look and this would require a complete rewrite of the GetResponse code in s2Member (active only with Pro) as the API calls are handled entirely differently. Workflow automations are becoming increasingly important to email marketing though and if you guys can fit it into your development schedule it would be wonderful. There is always the chance that GetResponse will stop supporting the v1.5 API altogether too.

[raamdev]

@patdumond Thanks so much for opening this issue and sharing your research. I'll mark this as something that needs to get done.

[patdumond]

Thanks, @raamdev. That's much appreciated.

[ronperkinsuk]

GetResponse has now removed support for v1.5 API as of October 2021, so this fix needs to be done ASAP.