Feature Request: PayID Aliases

[sappenin]

Create the concept of PayID aliases that will allow the user to create PayID aliases linked to the primary one.
For example, an operator could support alice$example.com using aliases like alice+savings$xpring.money and have that point to a particular underlying address.

See PayString/rfcs#26 for more details around this proposal.

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Are you willing to submit a pull request to implement this change?