Support per-SP reset "remember my choice" entries for the WAYF

Not for direct implementation! In the icebox for now.

In https://github.com/OpenConext/OpenConext-engineblock/issues/1956 we describe a feature where a user can specify per SP which IdP they want to use. On a next login to that SP, the preferred IdP will be used automatically without user interaction.

This story will allow a user to reset that choice for each individual SP.

The settings of which SP should use which IdP are stored in a cookie rememberedidps which is set on the main OpenCOnext domain (so if profile lives on https://profile.openconex.dev the cookie lives on the .openconext.dev domain).

The cookie is a base64-encoded deflated json structure like this:

{
  "https://sp_entityid_1": { "idp": "https://idp_entityid_1", "time": 1784534287 },
  "https://sp_entityid_2": { "idp": "https://idp_entityid_2", "time": 1784512345 }
}

In profile, the presence of this cookie should enable the following:

• In the list of Applications (https://profile.test2.surfconext.nl/my-services) show an icon for apps that have a "remember setting"

  

• After opening that item, show the remembered IdP choice underneath login details and provide the user with the option to reset it:

  

• After reset, show a feedback message:

  

The issue names no repository files or tests; start at the Applications page at /my-services and trace how application details and the rememberedidps cookie are handled. Done means showing a remember-setting indicator, displaying the remembered IdP with a per-SP reset option, and showing feedback after reset as illustrated in the screenshots.