Feat: Use alphanumeric for the validation code

[JeanneGrenet]

Closes #514

Description :

Following the Copenhagen Book we should use alphanumeric code for validation (without some specific characters) to prevent user errors. https://thecopenhagenbook.com/email-verification
Use the oslo library for this https://oslo.js.org/reference/crypto/generateRandomString

TASKS

• Update the generateCode() with generateRandomString()
• Use only specific characters instead of oslo alphabet()
• Update the PinInput to accept alphanumeric characters
• Test that we can connect with the alphanumeric code

[vercel]

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[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[AtamaHeitekava]

Testing done.
Everything seems to work as intended. I tried different actions (register, login, update email and delete account) that needed this code : each time the code is send and working as intended (if another code is given, it return an error) and the code given is alphanumeric.