refactor(audience-sdk): introduce AudienceArgumentMessages catalogue

Names the ArgumentException strings thrown from public SDK surfaces so user-code that reads .Message
stays in sync if a wording is tweaked in one site but not another.

- Log.cs: adds AudienceArgumentMessages with the Init / config validation entries
  (PublishableKeyRequired, PersistentDataPathRequired) and the typed-event ToProperties entries
  (ProgressionStatusRequired, ResourceFlow / Currency / AmountRequired, PurchaseValue /
  CurrencyInvalid, MilestoneReachedNameRequired).
- TypedEvents.cs: Progression / Resource / Purchase / MilestoneReached ArgumentException messages
  route through AudienceArgumentMessages.
- ImmutableAudience.cs: Init validation ArgumentException messages route through
  AudienceArgumentMessages.

Author: ImmutableJeffrey

src/Packages/Audience/Runtime/Events/TypedEvents.cs

@@ -84,7 +84,7 @@ public class Progression : IEvent
         public Dictionary<string, object> ToProperties()
         {
             if (Status is null)
-                throw new ArgumentException("Progression.Status is required. Set it before calling Track(IEvent).");
+                throw new ArgumentException(AudienceArgumentMessages.ProgressionStatusRequired);
 
             var props = new Dictionary<string, object>
             {
@@ -169,11 +169,11 @@ public class Resource : IEvent
         public Dictionary<string, object> ToProperties()
         {
             if (Flow is null)
-                throw new ArgumentException("Resource.Flow is required. Set it before calling Track(IEvent).");
+                throw new ArgumentException(AudienceArgumentMessages.ResourceFlowRequired);
             if (string.IsNullOrEmpty(Currency))
-                throw new ArgumentException("Resource.Currency is required. Set a non-empty string before calling Track(IEvent).");
+                throw new ArgumentException(AudienceArgumentMessages.ResourceCurrencyRequired);
             if (Amount is null)
-                throw new ArgumentException("Resource.Amount is required. Set it before calling Track(IEvent).");
+                throw new ArgumentException(AudienceArgumentMessages.ResourceAmountRequired);
 
             var props = new Dictionary<string, object>
             {
@@ -245,10 +245,9 @@ private static bool IsIso4217(string s)
         public Dictionary<string, object> ToProperties()
         {
             if (Currency == null || !IsIso4217(Currency))
-                throw new ArgumentException(
-                    $"Purchase.Currency '{Currency}' must be a three-letter uppercase ISO 4217 code");
+                throw new ArgumentException(AudienceArgumentMessages.PurchaseCurrencyInvalid(Currency));
             if (Value is null)
-                throw new ArgumentException("Purchase.Value is required. Set it before calling Track(IEvent).");
+                throw new ArgumentException(AudienceArgumentMessages.PurchaseValueRequired);
 
             var props = new Dictionary<string, object>
             {
@@ -284,7 +283,7 @@ public class MilestoneReached : IEvent
         public Dictionary<string, object> ToProperties()
         {
             if (string.IsNullOrEmpty(Name))
-                throw new ArgumentException("MilestoneReached.Name must not be null or empty");
+                throw new ArgumentException(AudienceArgumentMessages.MilestoneReachedNameRequired);
 
             return new Dictionary<string, object>
             {

src/Packages/Audience/Runtime/ImmutableAudience.cs

@@ -146,12 +146,12 @@ public static void Init(AudienceConfig config)
         {
             if (config == null) throw new ArgumentNullException(nameof(config));
             if (string.IsNullOrEmpty(config.PublishableKey))
-                throw new ArgumentException("PublishableKey is required", nameof(config));
+                throw new ArgumentException(AudienceArgumentMessages.PublishableKeyRequired, nameof(config));
 
             if (string.IsNullOrEmpty(config.PersistentDataPath))
                 config.PersistentDataPath = DefaultPersistentDataPathProvider?.Invoke();
             if (string.IsNullOrEmpty(config.PersistentDataPath))
-                throw new ArgumentException("PersistentDataPath is required", nameof(config));
+                throw new ArgumentException(AudienceArgumentMessages.PersistentDataPathRequired, nameof(config));
 
             // Normalize casing so dashboards aggregate consistently. The
             // DistributionPlatforms constants ship lowercase; a studio that

src/Packages/Audience/Runtime/Utility/Log.cs

@@ -43,6 +43,25 @@ private static void Emit(string line)
         }
     }
 
+    // ArgumentException messages thrown from public SDK methods.
+    internal static class AudienceArgumentMessages
+    {
+        // Init / config validation
+        internal const string PublishableKeyRequired = "PublishableKey is required";
+        internal const string PersistentDataPathRequired = "PersistentDataPath is required";
+
+        // Typed-event ToProperties validation
+        internal const string ProgressionStatusRequired = "Progression.Status is required. Set it before calling Track(IEvent).";
+        internal const string ResourceFlowRequired = "Resource.Flow is required. Set it before calling Track(IEvent).";
+        internal const string ResourceCurrencyRequired = "Resource.Currency is required. Set a non-empty string before calling Track(IEvent).";
+        internal const string ResourceAmountRequired = "Resource.Amount is required. Set it before calling Track(IEvent).";
+        internal const string PurchaseValueRequired = "Purchase.Value is required. Set it before calling Track(IEvent).";
+        internal const string MilestoneReachedNameRequired = "MilestoneReached.Name must not be null or empty";
+
+        internal static string PurchaseCurrencyInvalid(string? currency) =>
+            $"Purchase.Currency '{currency}' must be a three-letter uppercase ISO 4217 code";
+    }
+
     // Error messages we pass to AudienceConfig.OnError.
     internal static class AudienceErrorMessages
     {