satellite-provider/SatelliteProvider.Api/Validators/GlobalValidatorConfig.cs

using FluentValidation;

namespace SatelliteProvider.Api.Validators;

// AZ-795 / AZ-796: process-wide FluentValidation configuration shared by the
// API host and unit tests. Tests must call ApplyOnce() in their fixture setup
// so the property-name casing they assert against matches what the running
// API will produce — see `_docs/02_document/contracts/api/error-shape.md`
// invariant Inv-4 (camelCase paths in `errors` map).
public static class GlobalValidatorConfig
{
    private static readonly object _gate = new();
    private static bool _applied;

    public static void ApplyOnce()
    {
        lock (_gate)
        {
            if (_applied) return;

            ValidatorOptions.Global.PropertyNameResolver = (type, member, expression) =>
            {
                var name = member?.Name;
                if (string.IsNullOrEmpty(name)) return null;
                return char.ToLowerInvariant(name[0]) + name[1..];
            };

            _applied = true;
        }
    }
}