Use Degraded instead of Unhealthy in SystemUpdatesHealthCheck

[hishamco]

On the last OC standup meeting @sebastienros comment about why we are using HealthStatus.Unhealthy if there's a new update available and the system is still up & running, which is making sense. Changing the status to a less than HealthStatus.Unhealthy would be fine

FYI Seb, the terminologies might little bit different on Azure, where you need to restart the node

namespace Microsoft.Extensions.Diagnostics.HealthChecks
{
    /// <summary>
    /// Represents the reported status of a health check result.
    /// </summary>
    /// <remarks>
    /// <para>
    /// A status of <see cref="Unhealthy"/> should be considered the default value for a failing health check. Application
    /// developers may configure a health check to report a different status as desired.
    /// </para>
    /// <para>
    /// The values of this enum or ordered from least healthy to most healthy. So <see cref="HealthStatus.Degraded"/> is
    /// greater than <see cref="HealthStatus.Unhealthy"/> but less than <see cref="HealthStatus.Healthy"/>.
    /// </para>
    /// </remarks>
    public enum HealthStatus
    {
        /// <summary>
        /// Indicates that the health check determined that the component was unhealthy, or an unhandled
        /// exception was thrown while executing the health check.
        /// </summary>
        Unhealthy = 0,

        /// <summary>
        /// Indicates that the health check determined that the component was in a degraded state.
        /// </summary>
        Degraded = 1,

        /// <summary>
        /// Indicates that the health check determined that the component was healthy.
        /// </summary>
        Healthy = 2,
    }
}

So, I think it's fine now to use Unhealthy if there's something goes wrong such as the email service doesn't working or we can't connect to the database

[hishamco]

Backing to the SystemUpdatesHealthCheck if there's a new update it would be nice to notify the user that there's a new update - probably a patch release - so an action should be taken, even if the app is healthy