Intent to implement: Non-modal dismissable user notifications

[cramforce]

Implement a tag that can be shown conditionally for applicable users and that can be dismissed by users.

Usage

<amp-user-notification 
    layout=nodisplay
    data-dialog-id="some-dialog"
    data-show-if-href="https://external-host.com/show-dialog"
    data-dismiss-href="https://external-host.com/confirm">
   …arbitrary HTML…
   <button on="tap:amp-user-notification.dismiss()">Got it</button>
</amp-user-notification>

Showing the dialog

The new tag amp-user-notification always starts out in layout mode nodisplay (isn’t shown). Upon page load it makes a POST CORS XHR request to the URL given as data-show-if-href. It posts an ExternalCID that is specific for the string given as data-dialog-id as the POST argument “user_id”.

The POST request is expected to return a simple JSON document of the form
{"show_dialog": true}
or
{"show_dialog": false}

In case of the true response AMP switches the <amp-user-notification> tag to have container layout and displays it in a fixed positioned container at position (0, 0) and as wide as the screen.

Closing the dialog

A button or similar tag inside of the notification can be designated with on="tap:amp-user-notification.dismiss()" to dismiss the notification.
If the user taps that button the <amp-user-notification> is again switched to nodisplay mode and AMP makes a POST CORS XHR request to the URL given as data-dismiss-href. It posts an ExternalCID that is specific for the string given as data-dialog-id as the POST argument “user_id”.

The above POST request presents an opportunity for the publisher to store for the given “user_id” as to whether it should return true next time a request to data-show-if-href is made.

[cramforce]

See #871 for one possible use of this.

[cramforce]

@erwinmombay Assigned you. OK?

[erwinmombay]

@cramforce 👍

[rudygalfi]

@erwinmombay Trying to get a handle on when various features will land. Any estimate on this one?

[erwinmombay]

@rudygalfi almost done (thursday or friday at worst), talking to @dvoytenko about some technical details on implementation (since he's also working on some alert stuff). I think he had some concerns on this specific component.

[rudygalfi]

👍 thanks

[ericlindley-g]

@erwinmombay — can this be closed?

[erwinmombay]

@ericlindley-g i think we should be good here since we have issues for the follow ups. anyone feel free to reopen otherwise.