fix: allow webinterface schematic format to be detected

[PierreSchwang]

Overview

Fixes #2892

Description

Not completely happy with how it works - but that's just a limitation of the interface itself.
When not specifying the format, it'll be auto detected. Sadly, the interface outputs the command with the schem format specified (which now defaults to v3). But I've updated the exception handling to state that, if the schematic fails to load (the EOFException triggered, when loading a v2 schematic with the default schem was handled by the IOException block):

As I'd have to download the file either way when checking for the format, it's simply downloaded even if the format is specified. That way it can utilize the reset functionality of the underlying stream for the reader (v3 in particular). The Closer handles the deletion either way - so it shouldn't clog up anything nor be noticeable in any way.

### Submitter Checklist
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[PierreSchwang]

I thought about adding a check if the format schem is specified (as the schematic interface spits the command out with that format explicitly set) and check the format either way - but that felt quite wrong

[Feniksovich]

I thought about adding a check if the format schem is specified (as the schematic interface spits the command out with that format explicitly set) and check the format either way - but that felt quite wrong

I agree with that, but I'm also afraid most users don't pay so much attention to commands syntax, what the each argument means or what schematics schemas actually exist (I'm not sure if the syntax of /schem command is documented anywhere).

For now, on my end I monitor /schem command execution and display the message with exact instructions and commands that can be executed to workaround current loading behavior (e.g. suggesting try /schem load fast.2 url:<code>).

[PierreSchwang]

I thought about adding a check if the format schem is specified (as the schematic interface spits the command out with that format explicitly set) and check the format either way - but that felt quite wrong

I agree with that, but I'm also afraid most users don't pay so much attention to commands syntax, what the each argument means or what schematics schemas actually exist (I'm not sure if the syntax of /schem command is documented anywhere).

For now, on my end I monitor /schem command execution and display the message with exact instructions and commands that can be executed to workaround current loading behavior (e.g. suggesting try /schem load fast.2 url:<code>).

I guess it's already enough, that the more precise error is printed, when specifying the wrong format. That should help a bit - maybe (given the error is read)