RATIONALE
Simplify field management for mail / phone / sms flows. Make it working out
of the box, easier to use and tweak.
SPECIFICATIONS
In addition to finding the customer, sometimes we just want any partner on
a record, notably for VOIP. For that purpose we improve heuristic for
finding partner (fields or records). It introspects the model to find any
relational field towards res.partner. Note that as it is generic it does
not ensure the partner is a customer, just some partner.
Task-3422449 (Mail, Phone: Move and improve field helpers)
Prepares Task-36879 (Mail: Support MultiCompany Aliases)
Part-of: odoo/odoo#130468