Should the amp-user-notification component do a GET or POST request to the data-show-if-href url

[erwinmombay]

Got feedback from @dvoytenko on this (quote: a POST without user action is generally suspicious).

Currently I switched the request to a POST so that we're able to transmit the json data { ampUserId, elementId } to the server and it can determine wether to show the notification to the current visitor or not.

The alternative is to switch back to a GET request and transmit the data as query params.

/cc @dvoytenko @cramforce for input

[dvoytenko]

Additional thing that GET buys us is that we can inject query parameters via URL substitutions: https://github.com/ampproject/amphtml/blob/master/spec/amp-var-substitutions.md

I don't know if this is useful.

[erwinmombay]

@cramforce unless you have any objections, i'll switch this to a GET with the query params elementId and ampUserId keys.