Replace html/template with type-safe elem-go templating for OIDC
callback page. Improves consistency with other templates and provides
compile-time safety. All UI elements and styling preserved.
This change makes editing the generated command easier.
For example, after pasting into a terminal, the cursor position will be
near the username portion which requires editing.
* Changed all the HTML into go using go-elem
Created templates package in ./hscontrol/templates.
Moved the registerWebAPITemplate into the templates package as a function to be called.
Replaced the apple and windows html files with go-elem.
* update flake
Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>
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Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>
Co-authored-by: Kristoffer Dalby <kristoffer@tailscale.com>
