feat: HedgeDoc module(#168)

Reviewed-on: https://git.selfprivacy.org/SelfPrivacy/selfprivacy-nixos-config/pulls/168
Reviewed-by: Inex Code <inex.code@selfprivacy.org>
Co-authored-by: Thary <thary@riseup.net>
Co-committed-by: Thary <thary@riseup.net>

sp-modules/hedgedoc/hedgedocClientSecretAsFile.patch

@@ -0,0 +1,13 @@
+diff --git a/lib/web/auth/oauth2/index.js b/lib/web/auth/oauth2/index.js
+index b0ffa5e8a..01e16e152 100644
+--- a/lib/web/auth/oauth2/index.js
++++ b/lib/web/auth/oauth2/index.js
+@@ -134,7 +134,7 @@ passport.use(new OAuth2CustomStrategy({
+   authorizationURL: config.oauth2.authorizationURL,
+   tokenURL: config.oauth2.tokenURL,
+   clientID: config.oauth2.clientID,
+-  clientSecret: config.oauth2.clientSecret,
++  clientSecret: require("fs").readFileSync(config.oauth2.clientSecret, 'utf8').split("\n")[0],
+   callbackURL: config.serverURL + '/auth/oauth2/callback',
+   userProfileURL: config.oauth2.userProfileURL,
+   scope: config.oauth2.scope,