Collect a beacon through the pixel fallback

Take a beacon from the query string and answer with a 1x1 GIF.

What the tracker falls back to when it cannot POST. Unauthenticated: the collector hash in the URL names the application, as it does for the POST. The answer is the GIF whatever the beacon contained, so a browser never renders a broken image, and nothing about the outcome is reported back.

A pageview that arrives twice, once here and once by POST, is stored once.

curl -X GET 'https://api.fastmon.eu/c/string'

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