Cannot set Custom field regex via API

[fabricat]

Please confirm you have done the following before posting your bug report:

• (n/a) I have enabled debug mode
• I have read checked the Common Issues page

Describe the bug
When I use API to create a new custom field with regex validation, I get the error "format":["The selected format is invalid."].

To Reproduce
Steps to reproduce the behavior:

1. Go to https://snipe-it.readme.io/reference#fields-2
2. Fill the BODY PARAMS with:
   name="Regex test"
   element="text"
   format="regex:/^[0-9]{8}$/"
3. Check on the right panel, the cURL command should end like this:
   --data {"show_in_email":false,"field_encrypted":false,"element":"text","name":"Regex test","format":"regex:/^[0-9]{8}$/"}
4. Click on the Try It button
5. See error message (relative to the format field):
   "The selected format is invalid"

The same happens on my local Docker installation (image snipe/snipe-it:v5.1.4).

Expected behavior
The custom field should be correctly created.

Screenshots

Server (please complete the following information):

• Snipe-IT Version 5.1.4
• OS: Docker official image
• Web Server: Docker official image
• PHP Version: Docker official image

Desktop (please complete the following information):

• OS: Windows
• Browser: Chrome
• Version 87

Smartphone (please complete the following information):
n/a

Error Messages
The cURL output is:
{"status":"error","messages":{"format":["The selected format is invalid."]},"payload":null}

Additional context

• Fresh install
• Installed via Docker

[welcome]

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[viclou]

FD20573