Strict types in RemoteConfig

ts/RemoteConfig.ts

@@ -10,6 +10,7 @@ import { parseIntOrThrow } from './util/parseIntOrThrow';
 import { SECOND, HOUR } from './util/durations';
 import * as Bytes from './Bytes';
 import { uuidToBytes } from './util/uuidToBytes';
+import { dropNull } from './util/dropNull';
 import { HashType } from './types/Crypto';
 import { getCountryCode } from './types/PhoneNumber';
 
@@ -54,7 +55,7 @@ type ConfigValueType = {
   name: ConfigKeyType;
   enabled: boolean;
   enabledAt?: number;
-  value?: unknown;
+  value?: string;
 };
 export type ConfigMapType = {
   [key in ConfigKeyType]?: ConfigValueType;
@@ -105,7 +106,11 @@ export const refreshRemoteConfig = async (
   const oldConfig = config;
   config = newConfig.reduce((acc, { name, enabled, value }) => {
     const previouslyEnabled: boolean = get(oldConfig, [name, 'enabled'], false);
-    const previousValue: unknown = get(oldConfig, [name, 'value'], undefined);
+    const previousValue: string | undefined = get(
+      oldConfig,
+      [name, 'value'],
+      undefined
+    );
     // If a flag was previously not enabled and is now enabled,
     // record the time it was enabled
     const enabledAt: number | undefined =
@@ -115,7 +120,7 @@ export const refreshRemoteConfig = async (
       name: name as ConfigKeyType,
       enabled,
       enabledAt,
-      value,
+      value: dropNull(value),
     };
 
     const hasChanged =