provide help about the ELN instance

[kjappelbaum]

aiidalab-eln/aiidalab_eln/cheminfo/__init__.py

Line 30 in 1772dcd

description="ELN address:",

i think this is not necessarily clear to users. Do they have to provide http? https? www? do they have to provide the trailing eln? Where do they get this info.

I think we should add a help text with something like you can find the URL for the ELN instance in Tools -> Access Token.

Alternatively, we can also print it in the iframe

[kjappelbaum]

also, we should maybe sanitize trailing slashes and stuff like this. I can do parts of it in cheminfopy, but we would then need to handle Exceptions that are raised

[kjappelbaum]

working on the URL checks here cheminfo-py/cheminfopy#31