feat: add conditional registration fields js script

[andrey-canon]

Description:

This PR implements the current capability of the Bragi theme to add fields that are conditionally displayed based on the values of other fields. The instructions include the necessary settings for the expected behavior in the specific example below:

• If a user selects an occupation other than "employee," nothing will happen.
• If the user selects "employee," a new field called sector will appear.
• If the sector is different from "public," a text input will appear.

If the sector is "public," a field with limited options will appear, in this case using the value from the setting VALID_PUBLIC_SECTOR.

This example is specific to the current configuration. However, by modifying the settings, different conditional behaviors can be achieved.

How to test

1. Add the following settings

VALID_PUBLIC_SECTORS = [
    "saudi_post",
    "communications_and_information_technology_commission",
    "ministry_of_communications_and_information_technology",
    "other"
]
CONDITIONAL_REGISTRATION_FIELDS = {
    "occupation": {
        "dependent_fields": {
            "employee": [
                "sector",
            ],
        },
        "key": "occupation",
        "options": [
            "employee",
            "student",
            "unemployed",
        ],
    },
    "public_sector": {
        "alias": "specific_sector",
        "options": VALID_PUBLIC_SECTORS,
    },
    "sector": {
        "dependent_fields": {
            "non_profit": [
                "specific_sector",
            ],
            "private": [
                "specific_sector",
            ],
            "public": [
                "public_sector",
            ]
        },
        "options": [
            "public",
            "private",
            "non_profit",
        ],
    },
}
REGISTRATION_EXTRA_FIELDS["sector"] = "optional"
REGISTRATION_EXTRA_FIELDS["specific_sector"] = "optional"

2. Go to register page http://local.overhang.io:8000/register
3. Check that the behavior is the expected, watch video for reference

2025-08-11.16-48-35.mp4

[OmarIthawi]

Thanks Andrey :)

@johanseto @shadinaif we need two reviewers for this PR.

cc: @andrey-canon

[johanseto]

  o            o__ __o    ____o__ __o____   o          o  
 <|>          /v     v\    /   \   /   \   <|\        /|> 
 / \         />       <\        \o/        / \\o    o// \ 
 \o/       o/                    |         \o/ v\  /v \o/ 
  |       <|       _\__o__      < >         |   <\/>   |  
 / \       \\          |         |         / \        / \ 
 \o/         \         /         o         \o/        \o/ 
  |           o       o         <|          |          |  
 / \ _\o__/_  <\__ __/>         / \        / \        / \ 
                                                          
                                                          
                                                          

Working in my local env

Screencast.from.08-09-25.17.47.35.webm

Screencast.from.08-09-25.17.48.43.webm

[shadinaif]

Clean, thank you!