Fix use of media credentials for fetching/restoring media related data.

core-util-jvm/src/main/java/org/signal/core/util/StringExtensions.kt

@@ -5,6 +5,8 @@
 
 package org.signal.core.util
 
+import java.net.URLEncoder
+import java.nio.charset.StandardCharsets
 import kotlin.contracts.ExperimentalContracts
 import kotlin.contracts.contract
 
@@ -70,3 +72,10 @@ fun CharSequence?.isNotNullOrBlank(): Boolean {
   }
   return !this.isNullOrBlank()
 }
+
+/**
+ * Encode this string in a url-safe way with UTF-8 encoding.
+ */
+fun String.urlEncode(): String {
+  return URLEncoder.encode(this, StandardCharsets.UTF_8.name())
+}