Rewrite as a MailExtension

[kewisch]

Thunderbird now focuses on (MailExtensions)[https://developer.thunderbird.net/add-ons/mailextensions] for extension development. I'm rewriting this extension as a MailExtension, and at the same time building a MailExtensions API for calendaring. I'm not including all the done items, but here is whats left to do as of filing this bug.

UI

• Event dialog - move UI into frame MVP
• Event dialog - validate reminders
• New Calendar Dialog - make calendar creation pretty MVP
• Port Options UI abc3a41 MVP
• Make sure Event dialog asks to save a new event with no modifications (Bugzilla Bug 1568096) #11 has not regressed

Items

• Use of RFC3339 for LASTACK and SNOOZE-TIME MVP
• Ensure timezones work, our ical.js doesn't have a timezones registry MVP
• Organizer part of attendees or not
• Pref for disabling attendees
• Figure out if we can throw in parseEventStream
• deal with events that have DURATION instead of DTEND
• Support HTML descriptions (and port 6625aba) MVP

Calendars

• Throttling of requests
• Avoid hitting rate limiting (When deleting many events, Google's rate limiting kicks in #187)
• Conflict resolution MVP
• Deal with invitations and importing events MVP
• Disabling calendars on certain errors
• Ensure that network failures will trigger offline mode (see When proxy not set at ThB start, lightning/gdata-provider does nothing without any warning #163) MVP

Experiment

• Event dialog - API to deal with user changes. Frame should be able to react to that
• Create capabilities for UI, e.g. disabling attachments, attendees, privacy, etc
• Event dialog - ability to validate the event, extension should be able to say when something is wrong
• Reminder dialog - Provide some capabilities?
• Properties dialog - Capability to force readonly mode, don't allow changing in the calendar properties dialog
• Properties dialog - Capabilities w.r.t. refreshInterval. Minimum value? Provide list of values? Maximum value?
• Properties dialog - add an extension frame
• Addon calendar wizard - discuss more future proof way to trigger creation
• Activity Stream API?
• Validate capability names

Recurrence

• Verify etags for recurring events work MVP

Migration

• Migrating ICS calendars, setting googleCalendarName
• Notification/UI when migratable calendars happen
• Ensure properties such as disabled/color/etc are migrated

[kewisch]

Hey folks. I'm going to go ahead and lock this issue since I want to use it for tracking the rewrite. If you are experiencing any issues please file a separate one.