(Arc4u 6.1.18.x+) Disambiguate MessageCategory and align their definitions

[vvdb-architecture]

Both namespaces Arc4u.Diagnostics and Arc4u.ServiceModel contain an identically named public type MessageCategory.

In Arc4u.Diagnostics (assembly Arc4u.Standard.Diagnostics), this is defined as:

    /// <summary>
    /// Specifies the different categories of a <see cref="FaultMessage"/>.
    /// </summary>
    [DataContract]
    [Flags]
    public enum MessageCategory : short
    {
        /// <summary>
        /// A message dedicates for IT people.
        /// </summary>
        [EnumMember]
        Technical = 1,
        /// <summary>
        /// A message dedicates for IT and Business people.
        /// </summary>
        [EnumMember]
        Business = 2,

        /// <summary>
        /// For Monitoring purpose.
        /// </summary>
        [EnumMember]
        Monitoring = 4,
    }

In Arc4u.ServiceModel, (assembly Arc4u.Standard) this is defined as:

    /// <summary>
    /// Specifies the different categories of a <see cref="FaultMessage"/>.
    /// </summary>
    [DataContract]
    public enum MessageCategory : short
    {
        /// <summary>
        /// A message dedicates for IT people.
        /// </summary>
        [EnumMember]
        Technical = 0,
        /// <summary>
        /// A message dedicates for IT and Business people.
        /// </summary>
        [EnumMember]
        Business = 1,
    }

We should think about refactoring this and align the definitions, since it can only confuse.

One possibility would be to create a new assembly Arc4u.Standard.Exceptions that would hold what is now in Arc4u.ServiceModel and Arc4u.Exceptions namespaces of the Arc4u.Standard assembly. The Arc4u.Standard.Diagnostics assembly would then depend on this Arc4u.Standard.Exceptions assembly for its MessageCategory definition instead of defining it itself.