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Note that the ECI which had been used in the full /sky/cloud URL is not shown in the list. It was deleted before the screenshot was captured. That is because the specific value need not be known or shared at all for the shorter link to work. The engine will select the channel of type "web shortcut" with the name must in the short URL my.room and use that channel's ECI when it re-writes the short URL to produce the standard URL which the engine actually uses internally.
Having created the channel as specified, the short URL will now work.
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Notice that for events, the first part of the path in a shorter link can be chosen somewhat arbitrarily, because it becomes the EID in the (internally) rewritten longer link that actually is seen by the engine. In the case of queries, the first part of the path in the shorter link must exactly match the RID. In both cases, the first part of the path (immediately following the domain name and port (if present)) must match this regular expression: re#/[\w.-]*#, i.e. it must begin with a forward slash, followed by letters, digits, or the underscore, period, or hypen characters only.
If you are wondering why the ECI for the secret channel named "admin" is redacted in the image above, it is because this is the only channel that the pico has which is not fungible, which cannot be deleted without requiring the pico itself to also be deleted. So, even though the pico is running on an engine which I control, and which is running on a machine which I control, I'm not taking any chances.
This capability willn't be introduced into the engine until after its current version, 0.43.0 (at which time this paragraph will be removed, so savor it while it lasts).
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