feat(featureflags): improved feature flag handling [EE-4609] (#8222)

* updated and improved feature flags using new module

* merge init into parse

* update the package documentation

* better docs

* minor tidy

pkg/featureflags/featureflags.go

@@ -0,0 +1,98 @@
+/*
+	 Package featureflags implements feature flags for Portainer projects
+
+	 Feature flags are used to turn on features that are not production ready.
+	 Use the Parse function to enable feature flags and also the pass a list of
+	 available flags
+
+	   e.g.
+	    var SupportedFeatureFlags = []featureflags.Feature{
+			"my-feature",
+		}
+
+		func main() {
+			// parse cli flags
+
+			// pass cli flags and supported feature flags to featureflags.Parse
+			featureflags.Parse([]string{"my-feature"}, SupportedFeatureFlags)
+		}
+
+		...
+		if featureflags.IsEnabled("my-feature") {
+			// do something
+		}
+*/
+package featureflags
+
+import (
+	"os"
+	"strings"
+
+	"github.com/rs/zerolog/log"
+)
+
+// Feature represents a feature that can be enabled or disabled via feature flags
+type Feature string
+
+var featureFlags map[Feature]bool
+
+// String returns the string representation of a feature flag
+func (f Feature) String() string {
+	return string(f)
+}
+
+// IsEnabled returns true if the feature flag is enabled
+func IsEnabled(feat Feature) bool {
+	return featureFlags[feat]
+}
+
+// IsSupported returns true if the feature is supported
+func IsSupported(feat Feature) bool {
+	_, ok := featureFlags[feat]
+	return ok
+}
+
+// FeatureFlags returns a map of all feature flags.
+// this is useful in situations where you need to pass all feature flags to a REST handler
+// function
+func FeatureFlags() map[Feature]bool {
+	return featureFlags
+}
+
+func initSupportedFeatures(supportedFeatures []Feature) {
+	featureFlags = make(map[Feature]bool)
+	for _, feat := range supportedFeatures {
+		featureFlags[feat] = false
+	}
+}
+
+// Parse turns on feature flags
+// It accepts a list of feature flags as strings and a list of supported features.
+// It will also check for feature flags in the PORTAINER_FEATURE_FLAGS environment variable.
+// Multiple feature flags can be specified with the PORTAINER_FEATURE_FLAGS environment.
+// variable using a comma separated list. e.g. "PORTAINER_FEATURE_FLAGS=feature1,feature2".
+// If a feature flag is not supported, it will be logged and ignored.
+// If a feature flag is supported, it will be logged and enabled.
+func Parse(features []string, supportedFeatures []Feature) {
+	initSupportedFeatures(supportedFeatures)
+
+	env := os.Getenv("PORTAINER_FEATURE_FLAGS")
+	envFeatures := []string{}
+	if env != "" {
+		envFeatures = strings.Split(env, ",")
+	}
+	features = append(features, envFeatures...)
+
+	// loop through feature flags to check if they are supported
+	for _, feat := range features {
+		f := Feature(strings.ToLower(feat))
+		_, ok := featureFlags[f]
+		if !ok {
+			log.Warn().Str("feature", f.String()).Msgf("unknown feature flag")
+			continue
+		}
+
+		featureFlags[f] = true
+		log.Info().Str("feature", f.String()).Msg("enabling feature")
+	}
+}