Use study-level parameters for participant compensation/communication to improve family and researcher communication

# TL;DR

Participant communication systems could use existing study-level parameters like study email/contact and study name and possibly participant-level parameters (child name) to improve the study communication process for both researchers and families. This would allow the researcher to (1) specify a different email per study and (2) auto-fill/provide default text that gives families the context of the communication automatically rather than depending on researchers' time or forethought.

# Narrative

1. Change email addresses provided to participants in participant compensation/other messages to use the specific **study** email instead of the lab email. **Separate issue here:** https://github.com/lookit/lookit-api/issues/1351
- Currently, this is sourced from the lab email, meaning that researchers cannot use different emails for different studies. This is particularly an issue for multi-lab collaborations like Project GARDEN which need a different email for each study so each team can communicate with their participants directly.
- This allows researchers to provide families with the option to directly reply to an email that is monitored by the specific staff running a particular study.

2. Change emails sent to families to auto-populate the child name, study name, and PI contact for the study itself.
- It should be clear to families which study and child for which they are receiving compensation/other communication.
- I would be happy to draft suggestions on language for this after scoping is complete and how the default text itself would work and where it could be placed within the email (e.g. does it populate for the researcher and then they can edit it, is it shown to the researcher but not editable, is it not shown to the researcher at all).

# Implementation Notes
As always, I'm more than happy to help troubleshoot/brainstorm specific ways to implement these changes.

The issue names no files, tests, or entry points. Start by mapping the participant compensation and other family-message flows, then review how study-level and participant-level parameters are currently exposed; issue 1351 covers the separate study-email change. Done should include an agreed scope and default communication behavior for study name, child name, and PI contact.

Written by the indexing model from the issue text.