Slack: add some fixes and connect it all up

src/slack/token.ts

@@ -0,0 +1,12 @@
+export function normalizeSlackToken(raw?: string): string | undefined {
+  const trimmed = raw?.trim();
+  return trimmed ? trimmed : undefined;
+}
+
+export function resolveSlackBotToken(raw?: string): string | undefined {
+  return normalizeSlackToken(raw);
+}
+
+export function resolveSlackAppToken(raw?: string): string | undefined {
+  return normalizeSlackToken(raw);
+}