Mollie API 4.4.0.0

New features:

• Add support for the cancelUrl, method, locale and testmode properties when updating a payment.
• Improve support for multi tenant setups, where the API / access key is not a static value. Example usage:
  When registering dependencies:

builder.Services.AddMollieApi(options => {
    //options.ApiKey = builder.Configuration["MySecretManagerMollie:ApiKey"]!;
    options.SetCustomMollieSecretManager<TenantSecretManager>();
    options.RetryPolicy = MollieHttpRetryPolicies.TransientHttpErrorRetryPolicy();
});

Custom secret manager for multi-tenant setup:

public class TenantSecretManager : IMollieSecretManager {
    private readonly ITenantService _tenantService;

    public string GetBearerToken() => _tenantService.GetCurrentTenant().ApiKey;
}

Bugfixes:

• Set PaymentLinkResponse.Amount property from required to optional nullable, since it possible to create a PaymentLink without an amount.
• Change OAuth authorize URL from www.mollie.com to my.mollie.com. Big thanks to @fjbender for the PR
• Update all links still pointing to api.mollie.nl to api.mollie.com