Need a notification system for notable events

[b1conrad]

Initial plan is to have a way to send an email notification that something interesting has happened wrt a participant's pico.

Strategy is to have each byname app identify such events and raise a byname_notification:status event on the pico's event bus.

If the participant has installed an app that reacts to that event, it could then send an email message, or take some other action, under the participant's control.

There is a module, com.mailjet.sdk that can be installed/configured to actually send an email message, using an account established by the participant.

[b1conrad]

I propose we take inspiration from Phil Windley's blog post on Notifications.

[b1conrad]

With this commit and the few preceding it, we received a couple of email notifications of notable events. Still needs some finessing, but it basically works now.

[b1conrad]

These are the steps that a participant must follow to receive notifications of relationship events:

1. Sign up for a developer account with mailjet
2. Obtain and save* the secrets, adding to them your email address and name
3. Install the com.mailjet.sdk ruleset using the "Technical" section of the "Manage apps" page, configuring it with the secrets
4. Add the org.picostack.observer app
5. Visit its page and register the desired email address to receive notifications
6. Thereafter, when notable relationship events occur, the participant will receive an email message

*the format to save them in is as follows:

{"api_key":"s1","secret_key":"s2","email":"s3","name":"s4"}

where s1 is the API key given by mailjet, s2 is the secret key that they show just one time after you generate it, s3 is the email address of your account with mailjet (or some other email address that they have approved as the sender), and s4 is the name you want to use as the sender.

[b1conrad]

Notice that I am working very hard here to not become yet another administrative system. It would be easy, and easier for the user, if we just signed up for a paid plan with mailjet and had the byname system send the email messages. But the principle is that we are providing a hosting service for picos which are owned by participants.

Furthermore, all byname does is raise byname_notification:status events when the notable relationship events occur. It is up to the participant to decide what to do about the events. Using the rulesets provided by PicoStack.org (as described in this blog post) is just one option.