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/microsoft.tsx

@@ -0,0 +1,18 @@
+import type { SVGProps } from "react";
+
+export function MicrosoftIcon(props: SVGProps<SVGSVGElement>) {
+  return (
+    <svg
+      xmlns="http://www.w3.org/2000/svg"
+      width="2em"
+      height="2em"
+      viewBox="0 0 256 256"
+      {...props}
+    >
+      <path fill="#f1511b" d="M121.666 121.666H0V0h121.666z"></path>
+      <path fill="#80cc28" d="M256 121.666H134.335V0H256z"></path>
+      <path fill="#00adef" d="M121.663 256.002H0V134.336h121.663z"></path>
+      <path fill="#fbbc09" d="M256 256.002H134.335V134.336H256z"></path>
+    </svg>
+  );
+}