feat: multiple oauth providers (#355)

* feat: add flag decoder (candidate)

* refactor: finalize flags decoder

* feat: add env decoder

* feat: add oauth config parsing logic

* feat: implement backend logic for multiple oauth providers

* feat: implement multiple oauth providers in the frontend

* feat: add some default icons

* chore: add credits for parser

* feat: style oauth auto redirect screen

* fix: bot suggestions

* refactor: rework decoders using simpler and more efficient pattern

* refactor: rework oauth name database migration

frontend/src/components/icons/pocket-id.tsx

@@ -0,0 +1,20 @@
+import type { SVGProps } from "react";
+
+export function PocketIDIcon(props: SVGProps<SVGSVGElement>) {
+  return (
+    <svg
+      xmlns="http://www.w3.org/2000/svg"
+      xmlSpace="preserve"
+      width={512}
+      height={512}
+      viewBox="0 0 512 512"
+      {...props}
+    >
+      <circle cx="256" cy="256" r="256" />
+      <path
+        d="M268.6 102.4c64.4 0 116.8 52.4 116.8 116.7 0 25.3-8 49.4-23 69.6-14.8 19.9-35 34.3-58.4 41.7l-6.5 2-15.5-76.2 4.3-2c14-6.7 23-21.1 23-36.6 0-22.4-18.2-40.6-40.6-40.6S228 195.2 228 217.6c0 15.5 9 29.8 23 36.6l4.2 2-25 153.4h-69.5V102.4z"
+        className="fill-white"
+      />
+    </svg>
+  );
+}