Slight rendering issue when creating a pin with a description containing some unicode characters

[Lucas-C]

Observed with the following unicode characters:

• \xcc\x80, \xcc\x81 & \xcc\x82 : cf. https://www.utf8-chartable.de/unicode-utf8-table.pl?start=768&names=-&utf8=string-literal
• \xc2\xab & \xc2\xbb : cf. https://www.utf8-chartable.de/unicode-utf8-table.pl?start=128&number=128&utf8=string-literal&unicodeinhtml=hex
• \xe2\x80\x99 : cf. https://www.fileformat.info/info/unicode/char/2019/index.htm

Currently those characters are replaced by ? characters in the description.
We should:

1. add tests for those cases in the backend
2. handle those characters properly, or at least trigger a warning for the user that their description contains non-standard characters