fix: mark FeedbackBase default constructor as obsolete

There are situations now where feedbacks in the feedback collection
can be used to update things on UIs. If the feedback doesn't have a key, it can't
be used for this purpose.

src/PepperDash.Essentials.Core/Feedbacks/BoolFeedback.cs

@@ -42,6 +42,7 @@ namespace PepperDash.Essentials.Core
         /// it will NOT reflect an actual value from a device until <seealso cref="FireUpdate"/> has been called
         /// </remarks>
         /// <param name="valueFunc">Delegate to invoke when this feedback needs to be updated</param>
+        [Obsolete("use constructor with Key parameter. This constructor will be removed in a future version")]
         public BoolFeedback(Func<bool> valueFunc)
             : this(null, valueFunc)
         {

src/PepperDash.Essentials.Core/Feedbacks/FeedbackBase.cs

@@ -9,45 +9,54 @@ using PepperDash.Core;
 
 namespace PepperDash.Essentials.Core
 {
-	public abstract class Feedback : IKeyed
-	{
-		public event EventHandler<FeedbackEventArgs> OutputChange;
+    /// <summary>
+    /// Base class for all feedback types
+    /// </summary>
+    public abstract class Feedback : IKeyed
+    {
+        /// <summary>
+        /// Occurs when the output value changes
+        /// </summary>
+        public event EventHandler<FeedbackEventArgs> OutputChange;
 
         /// <summary>
         /// Gets or sets the Key
         /// </summary>
         public string Key { get; private set; }
 
-  /// <summary>
-  /// Gets or sets the BoolValue
-  /// </summary>
-  /// <inheritdoc />
-		public virtual bool BoolValue { get { return false; } }
-  /// <summary>
-  /// Gets or sets the IntValue
-  /// </summary>
-		public virtual int IntValue { get { return 0; } }
-  /// <summary>
-  /// Gets or sets the StringValue
-  /// </summary>
-		public virtual string StringValue { get { return ""; } }
+        /// <summary>
+        /// Gets or sets the BoolValue
+        /// </summary>
+        /// <inheritdoc />
+        public virtual bool BoolValue { get { return false; } }
+        /// <summary>
+        /// Gets or sets the IntValue
+        /// </summary>
+        public virtual int IntValue { get { return 0; } }
+        /// <summary>
+        /// Gets or sets the StringValue
+        /// </summary>
+        public virtual string StringValue { get { return ""; } }
         /// <summary>
         /// Gets or sets the SerialValue
         /// </summary>
         public virtual string SerialValue { get { return ""; } }
 
-  /// <summary>
-  /// Gets or sets the InTestMode
-  /// </summary>
-		public bool InTestMode { get; protected set; }
+        /// <summary>
+        /// Gets or sets the InTestMode
+        /// </summary>
+        public bool InTestMode { get; protected set; }
 
-		/// <summary>
-		/// Base Constructor - empty
-		/// </summary>
-		protected Feedback()
-		{
-		}
+        /// <summary>
+        /// Base Constructor - empty
+        /// </summary>
+        [Obsolete("use constructor with Key parameter. This constructor will be removed in a future version")]
+        protected Feedback() : this(null) { }
 
+        /// <summary>
+        /// Constructor with Key parameter
+        /// </summary>
+        /// <param name="key">The key for the feedback</param>
         protected Feedback(string key)
         {
             if (key == null)
@@ -58,27 +67,27 @@ namespace PepperDash.Essentials.Core
 
 
 
-  /// <summary>
-  /// ClearTestValue method
-  /// </summary>
-		public void ClearTestValue()
-		{
-			InTestMode = false;
-			FireUpdate();
-		}
+        /// <summary>
+        /// ClearTestValue method
+        /// </summary>
+        public void ClearTestValue()
+        {
+            InTestMode = false;
+            FireUpdate();
+        }
 
-		/// <summary>
-		/// Fires an update synchronously
-		/// </summary>
-		public abstract void FireUpdate();
+        /// <summary>
+        /// Fires an update synchronously
+        /// </summary>
+        public abstract void FireUpdate();
 
-		/// <summary>
-		/// Fires the update asynchronously within a CrestronInvoke
-		/// </summary>
-		public void InvokeFireUpdate()
-		{
-			CrestronInvoke.BeginInvoke(o => FireUpdate());
-		}
+        /// <summary>
+        /// Fires the update asynchronously within a CrestronInvoke
+        /// </summary>
+        public void InvokeFireUpdate()
+        {
+            CrestronInvoke.BeginInvoke(o => FireUpdate());
+        }
 
         /// <summary>
         /// Helper method that fires event. Use this intstead of calling OutputChange
@@ -103,5 +112,5 @@ namespace PepperDash.Essentials.Core
         {
             if (OutputChange != null) OutputChange(this, new FeedbackEventArgs(value));
         }
-	}
+    }
 }

src/PepperDash.Essentials.Core/Feedbacks/SerialFeedback.cs

@@ -13,7 +13,7 @@ namespace PepperDash.Essentials.Core
     /// </summary>
     public class SerialFeedback : Feedback
     {
-        public override string SerialValue { get { return _SerialValue; } } 
+        public override string SerialValue { get { return _SerialValue; } }
         string _SerialValue;
 
         //public override eCueType Type { get { return eCueType.Serial; } }
@@ -25,6 +25,7 @@ namespace PepperDash.Essentials.Core
 
         List<StringInputSig> LinkedInputSigs = new List<StringInputSig>();
 
+        [Obsolete("use constructor with Key parameter. This constructor will be removed in a future version")]
         public SerialFeedback()
         {
         }

src/PepperDash.Essentials.Core/Feedbacks/StringFeedback.cs

@@ -38,6 +38,7 @@ namespace PepperDash.Essentials.Core
         /// it will NOT reflect an actual value from a device until <seealso cref="FireUpdate"/> has been called
         /// </remarks>
         /// <param name="valueFunc">Delegate to invoke when this feedback needs to be updated</param>
+        [Obsolete("use constructor with Key parameter. This constructor will be removed in a future version")]
         public StringFeedback(Func<string> valueFunc)
             : this(null, valueFunc)
         {