refactor: share allow-from merge and sender-id checks

src/channels/allow-from.ts

@@ -0,0 +1,34 @@
+export function mergeAllowFromSources(params: {
+  allowFrom?: Array<string | number>;
+  storeAllowFrom?: string[];
+}): string[] {
+  return [...(params.allowFrom ?? []), ...(params.storeAllowFrom ?? [])]
+    .map((value) => String(value).trim())
+    .filter(Boolean);
+}
+
+export function firstDefined<T>(...values: Array<T | undefined>) {
+  for (const value of values) {
+    if (typeof value !== "undefined") {
+      return value;
+    }
+  }
+  return undefined;
+}
+
+export function isSenderIdAllowed(
+  allow: { entries: string[]; hasWildcard: boolean; hasEntries: boolean },
+  senderId: string | undefined,
+  allowWhenEmpty: boolean,
+): boolean {
+  if (!allow.hasEntries) {
+    return allowWhenEmpty;
+  }
+  if (allow.hasWildcard) {
+    return true;
+  }
+  if (!senderId) {
+    return false;
+  }
+  return allow.entries.includes(senderId);
+}