[PM-2282] Make feature flags type safe (#8612)

Refactors the feature flags in ConfigService to be type safe. It also moves the default value to a centralized location rather than the caller defining it. This ensures consistency across the various places they are used.

libs/common/src/enums/feature-flag.enum.ts

@@ -1,3 +1,8 @@
+/**
+ * Feature flags.
+ *
+ * Flags MUST be short lived and SHALL be removed once enabled.
+ */
 export enum FeatureFlag {
   BrowserFilelessImport = "browser-fileless-import",
   ItemShare = "item-share",
@@ -13,5 +18,32 @@ export enum FeatureFlag {
   EnableDeleteProvider = "AC-1218-delete-provider",
 }
 
-// Replace this with a type safe lookup of the feature flag values in PM-2282
-export type FeatureFlagValue = number | string | boolean;
+export type AllowedFeatureFlagTypes = boolean | number | string;
+
+// Helper to ensure the value is treated as a boolean.
+const FALSE = false as boolean;
+
+/**
+ * Default value for feature flags.
+ *
+ * DO NOT enable previously disabled flags, REMOVE them instead.
+ * We support true as a value as we prefer flags to "enable" not "disable".
+ */
+export const DefaultFeatureFlagValue = {
+  [FeatureFlag.BrowserFilelessImport]: FALSE,
+  [FeatureFlag.ItemShare]: FALSE,
+  [FeatureFlag.FlexibleCollectionsV1]: FALSE,
+  [FeatureFlag.VaultOnboarding]: FALSE,
+  [FeatureFlag.GeneratorToolsModernization]: FALSE,
+  [FeatureFlag.KeyRotationImprovements]: FALSE,
+  [FeatureFlag.FlexibleCollectionsMigration]: FALSE,
+  [FeatureFlag.ShowPaymentMethodWarningBanners]: FALSE,
+  [FeatureFlag.EnableConsolidatedBilling]: FALSE,
+  [FeatureFlag.AC1795_UpdatedSubscriptionStatusSection]: FALSE,
+  [FeatureFlag.UnassignedItemsBanner]: FALSE,
+  [FeatureFlag.EnableDeleteProvider]: FALSE,
+} satisfies Record<FeatureFlag, AllowedFeatureFlagTypes>;
+
+export type DefaultFeatureFlagValueType = typeof DefaultFeatureFlagValue;
+
+export type FeatureFlagValueType<Flag extends FeatureFlag> = DefaultFeatureFlagValueType[Flag];