[PM-19287] Feature flag for encrypt service (#13894)

* Extract getFeatureFlagValue to pure function

Co-authored-by: Matt Gibson <mgibson@bitwarden.com>

* Add broadcasting abstractions and OnServerConfigChange interface.

Co-authored-by: Matt Gibson <mgibson@bitwarden.com>

* Add implementation of onServerConfigChange on encrypt services

Co-authored-by: Matt Gibson <mgibson@bitwarden.com>

* Add onServerConfigChange implementation for encrypt worker

Co-authored-by: Matt Gibson <mgibson@bitwarden.com>

* Wire up broadcasting in dependency injection

Co-authored-by: Matt Gibson <mgibson@bitwarden.com>

* Add unit tests

* Handle subscribing for onServerConfigChange in init services

---------

Co-authored-by: Matt Gibson <mgibson@bitwarden.com>

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

@@ -0,0 +1,38 @@
+import { mock } from "jest-mock-extended";
+
+import { ServerConfig } from "../platform/abstractions/config/server-config";
+
+import { getFeatureFlagValue, FeatureFlag, DefaultFeatureFlagValue } from "./feature-flag.enum";
+
+describe("getFeatureFlagValue", () => {
+  const testFlag = Object.values(FeatureFlag)[0];
+  const testFlagDefaultValue = DefaultFeatureFlagValue[testFlag];
+
+  it("returns default flag value when serverConfig is null", () => {
+    const result = getFeatureFlagValue(null, testFlag);
+    expect(result).toBe(testFlagDefaultValue);
+  });
+
+  it("returns default flag value when serverConfig.featureStates is undefined", () => {
+    const serverConfig = {} as ServerConfig;
+    const result = getFeatureFlagValue(serverConfig, testFlag);
+    expect(result).toBe(testFlagDefaultValue);
+  });
+
+  it("returns default flag value when the feature flag is not in serverConfig.featureStates", () => {
+    const serverConfig = mock<ServerConfig>();
+    serverConfig.featureStates = {};
+
+    const result = getFeatureFlagValue(serverConfig, testFlag);
+    expect(result).toBe(testFlagDefaultValue);
+  });
+
+  it("returns the flag value from serverConfig.featureStates when the feature flag exists", () => {
+    const expectedValue = true;
+    const serverConfig = mock<ServerConfig>();
+    serverConfig.featureStates = { [testFlag]: expectedValue };
+
+    const result = getFeatureFlagValue(serverConfig, testFlag);
+    expect(result).toBe(expectedValue);
+  });
+});