Fix type of explicit parameters (#219)

Explicit parameters are an array of strings everywhere else. Because Go stores it as a map, persisted assignments for layers cannot be shared across SDKs.

This is a breaking change for anyone using the old schema

https://app.graphite.dev/github/pr/statsig-io/kong/2487/Add-test-coverage-for-additional-fields-in-sticky-values

evaluator.go

@@ -22,7 +22,7 @@ type evalResult struct {
 	SecondaryExposures            []SecondaryExposure    `json:"secondary_exposures"`
 	UndelegatedSecondaryExposures []SecondaryExposure    `json:"undelegated_secondary_exposures"`
 	ConfigDelegate                string                 `json:"config_delegate"`
-	ExplicitParameters            map[string]bool        `json:"explicit_parameters"`
+	ExplicitParameters            []string               `json:"explicit_parameters"`
 	EvaluationDetails             *EvaluationDetails     `json:"evaluation_details,omitempty"`
 	IsExperimentGroup             *bool                  `json:"is_experiment_group,omitempty"`
 }
@@ -429,12 +429,7 @@ func (e *evaluator) evalDelegate(user User, rule configRule, exposures []Seconda
 	result.ConfigDelegate = rule.ConfigDelegate
 	result.SecondaryExposures = e.cleanExposures(append(exposures, result.SecondaryExposures...), context.Hash)
 	result.UndelegatedSecondaryExposures = exposures
-
-	explicitParams := map[string]bool{}
-	for _, s := range config.ExplicitParameters {
-		explicitParams[s] = true
-	}
-	result.ExplicitParameters = explicitParams
+	result.ExplicitParameters = config.ExplicitParameters
 	return result
 }
 

logger.go

@@ -230,7 +230,12 @@ func (l *logger) getLayerExposureWithEvaluationDetails(
 	context *logContext) *ExposureEvent {
 	allocatedExperiment := ""
 	exposures := evalResult.UndelegatedSecondaryExposures
-	isExplicit := evalResult.ExplicitParameters[parameterName]
+	isExplicit := false
+	for _, s := range evalResult.ExplicitParameters {
+		if s == parameterName {
+			isExplicit = true
+		}
+	}
 
 	if isExplicit {
 		allocatedExperiment = evalResult.ConfigDelegate

user_persistent_storage_interface.go

@@ -10,7 +10,7 @@ type StickyValues struct {
 	SecondaryExposures            []SecondaryExposure    `json:"secondary_exposures"`
 	Time                          int64                  `json:"time"`
 	ConfigDelegate                string                 `json:"config_delegate,omitempty"`
-	ExplicitParameters            map[string]bool        `json:"explicit_parameters,omitempty"`
+	ExplicitParameters            []string               `json:"explicit_parameters,omitempty"`
 	UndelegatedSecondaryExposures []SecondaryExposure    `json:"undelegated_secondary_exposures"`
 }