Improve user ID validation error message with field name

Co-authored-by: jonathan <jonathan@taplytics.com>

Author: cursoragent

lib/devcycle-ruby-server-sdk/api/dev_cycle_provider.rb

@@ -49,14 +49,18 @@ def self.user_from_openfeature_context(context)
       end
       args = {}
       user_id = nil
+      user_id_field = nil
 
       # Priority order: targeting_key -> user_id -> userId
       if context.field('targeting_key')
         user_id = context.field('targeting_key')
+        user_id_field = 'targeting_key'
       elsif context.field('user_id')
         user_id = context.field('user_id')
+        user_id_field = 'user_id'
       elsif context.field('userId')
         user_id = context.field('userId')
+        user_id_field = 'userId'
       end
 
       # Validate user_id is present and is a string
@@ -65,7 +69,7 @@ def self.user_from_openfeature_context(context)
       end
 
       unless user_id.is_a?(String)
-        raise ArgumentError, "User ID must be a string, got #{user_id.class}"
+        raise ArgumentError, "User ID field '#{user_id_field}' must be a string, got #{user_id.class}"
       end
 
       # Check after type validation to avoid NoMethodError on non-strings

spec/devcycle_provider_spec.rb

@@ -16,21 +16,21 @@
       context = OpenFeature::SDK::EvaluationContext.new(targeting_key: 123)
       expect {
         DevCycle::Provider.user_from_openfeature_context(context)
-      }.to raise_error(ArgumentError, "User ID must be a string, got Integer")
+      }.to raise_error(ArgumentError, "User ID field 'targeting_key' must be a string, got Integer")
     end
 
     it 'raises error when user_id is not a string' do
       context = OpenFeature::SDK::EvaluationContext.new(user_id: 123)
       expect {
         DevCycle::Provider.user_from_openfeature_context(context)
-      }.to raise_error(ArgumentError, "User ID must be a string, got Integer")
+      }.to raise_error(ArgumentError, "User ID field 'user_id' must be a string, got Integer")
     end
 
     it 'raises error when userId is not a string' do
       context = OpenFeature::SDK::EvaluationContext.new(userId: 123)
       expect {
         DevCycle::Provider.user_from_openfeature_context(context)
-      }.to raise_error(ArgumentError, "User ID must be a string, got Integer")
+      }.to raise_error(ArgumentError, "User ID field 'userId' must be a string, got Integer")
     end
 
     it 'raises error when targeting_key is nil' do