added option to send invite to an address

The admin page now has the option to send an invite to an email address.
Since there are now two email types (invites and pw resets), the new
sections have been added to config.ini, and email_template and
email_plaintext have been renamed to email_html and email_text
respectively.

jellyfin_accounts/web.py

@@ -1,3 +1,4 @@
+import json
 from pathlib import Path
 from flask import Flask, send_from_directory, render_template
 from __main__ import config, app, g
@@ -31,11 +32,23 @@ from jellyfin_accounts.web_api import checkInvite
 def inviteProxy(path):
     if checkInvite(path):
         log.info(f'Invite {path} used to request form')
+        try:
+            with open(config['files']['invites'], 'r') as f:
+                invites = json.load(f)
+        except (FileNotFoundError, json.decoder.JSONDecodeError):
+            invites = {'invites': []}
+        for invite in invites['invites']:
+            if invite['code'] == path:
+                try:
+                    email = invite['email']
+                except KeyError:
+                    email = ""
         return render_template('form.html',
                                contactMessage=config['ui']['contact_message'],
                                helpMessage=config['ui']['help_message'],
                                successMessage=config['ui']['success_message'],
-                               jfLink=config['jellyfin']['server'])
+                               jfLink=config['jellyfin']['server'],
+                               email=email)
     elif 'admin.html' not in path and 'admin.html' not in path:
         return app.send_static_file(path)
     else: