Allow users to edit project digest and alerts settings

[amberrignell]

User story

As a project user, I would like to edit the frequency of my project digest and alerts, so that I can be notified on failures and get a summary of my project activity at my desired frequency.

Details

Context: issues 583 and 581 added the functionality to send users project digests and alerts on run failures at different frequencies.

See rough sketch below for guidance:

Implementation notes

N/A - @stuartc please read through but since this is mostly UI I don't expect many notes, just an estimate.

Release notes

• A user can enable/disable realtime alerts for a project.
• A user can edit the frequency at which they receive a project digest. (Possible values are never, daily, weekly and monthly)

User acceptance criteria

• In project settings > collaboration there is both a "digest" and a "realtime alerts" column
• A viewer, editor, admin or owner can edit THEIR OWN digest and alerts frequency: in the row next to their name, digest and realtime alerts are dropdowns that display the current value set for digest and realtime alerts.
• When an editor clicks the dropdown for digest, they can select from 'never', 'daily', 'weekly' and 'monthly'.
• When an editor clicks the dropdown for realtime alerts, they can select from "enabled" or "disabled"
• A viewer, editor, admin, owner can ONLY edit their own digest and realtime alerts settings. The digest and realtime alerts values displayed for other users in the 'collaboration' section are read-only.

@taylordowns2000 this is where we need to start thinking about roles ... should a viewer be able to receive notifications and project digests ? And if not then we should set the default values accordingly. Will update the release notes accordingly after we've discussed. @amberrignell , everyone on a project should be able to edit their own notifications (seems like a good start) but we should implement these permissions via the permissions module anyway — and later we may add the ability for an admin/owner to edit the notifications settings of other people who belong to their project.

[taylordowns2000]

@amberrignell , small changes made to the spec above. Looks great.