Auto-follow existing server admins when a new user registers

Hop-State: A_06FPE85XGRGM7FD155BAF78
Hop-Proposal: R_06FPE85ATWMCJ2G1HP9SMZR
Hop-Task: T_06FPE7FQ3T1G2VXH0TY9SR0
Hop-Attempt: AT_06FPE7FQ3RRTGK6K7VYESAR

src/lib/auth/admin-config.ts

@@ -0,0 +1,16 @@
+export function configuredAdminEmails(value = process.env.ADMIN_EMAILS): string[] {
+    return [...new Set(
+        (value || '')
+            .split(',')
+            .map((email) => email.trim().toLowerCase())
+            .filter(Boolean)
+    )];
+}
+
+export function isConfiguredAdminEmail(
+    email: string | null | undefined,
+    value = process.env.ADMIN_EMAILS
+): boolean {
+    if (!email) return false;
+    return configuredAdminEmails(value).includes(email.toLowerCase());
+}