[ACTION] Add Sendoso Core API endpoints

[s0s0physm]

Is there a specific app these actions are for?

Sendoso

Please provide a link to the relevant API docs for the specific service / operation.

https://developer.sendoso.com/rest-api/overview/introduction

1. Users: Get Current User, Get All Users, Invite New User
2. Teams: Get All Team Groups, Get All Team Group Users
3. Campaign (Touches): Get All Campaigns, Get Campaign
4. Sends: Retreive All Sends
   - Create Sends/Physical Gifts: Send Physical Gift, Send Physical Gift with Address Collection
   - Create Sends/eGifts*: Send eGift via Sendoso, Generate eGift Links

[s0s0physm]

@GTFalcao - all of endpoints, except for invite-new-user, are included in this PR. Updated the issue details to reflect this.