Avoid "Freesound" username restriction workarounds

[qubodup]

Regarding #2008
The following characters can be used to create a username that looks like it has "Freesound" in the name:

ѕ U+0455 : CYRILLIC SMALL LETTER DZE
е U+0435 : CYRILLIC SMALL LETTER IE
о U+043E : CYRILLIC SMALL LETTER O

also:

E → Cyrillic Ie (Е, U+0415)
Example: FRЕЕSOUND

O → Cyrillic O (О, U+041E)
Example: FREESОUND

E → Greek Epsilon (Ε, U+0395)
Example: FRΕΕSOUND

O → Greek Omicron (Ο, U+039F)
Example: FREESΟUND

N → Greek Nu (Ν, U+039D)
Example: FREESOUΝD

Successful attempt: https://freesound.org/people/fr%D0%B5%D0%B5s%D0%BEundtest222/

https://www.babelstone.co.uk/Unicode/whatisit.html shows:

U+0066 : LATIN SMALL LETTER F
U+0072 : LATIN SMALL LETTER R
U+0435 : CYRILLIC SMALL LETTER IE
U+0435 : CYRILLIC SMALL LETTER IE
U+0073 : LATIN SMALL LETTER S
U+043E : CYRILLIC SMALL LETTER O
U+0075 : LATIN SMALL LETTER U
U+006E : LATIN SMALL LETTER N
U+0064 : LATIN SMALL LETTER D
U+0074 : LATIN SMALL LETTER T
U+0065 : LATIN SMALL LETTER E
U+0073 : LATIN SMALL LETTER S
U+0074 : LATIN SMALL LETTER T
U+0032 : DIGIT TWO
U+0032 : DIGIT TWO
U+0032 : DIGIT TWO

PS: changed it to FRЕЕSOUNDtest222 to test visuals of having had more than 1 different username in the past.

[alastair]

amazing!

I hope that the switch in #1860 will resolve this issue, which deals with "normalizing" names into only a-z/ascii characters. Putting the link here so that we can review this bug once we implement it