[PM-5972] add subaddress generator strategy (#7897)

libs/common/src/tools/generator/username/subaddress-generator-options.ts

@@ -0,0 +1,10 @@
+/** Settings supported when generating an email subaddress */
+export type SubaddressGenerationOptions = {
+  type?: "random" | "website-name";
+  email?: string;
+};
+
+/** The default options for email subaddress generation. */
+export const DefaultSubaddressOptions: Partial<SubaddressGenerationOptions> = Object.freeze({
+  type: "random",
+});