Improved config options for OIDC (#9)

Added many new configuration options, including claim configuration and client_secret/confidential client support. Also enables user linking & creates person entries upon first sign in.

custom_components/auth_oidc/views/templates/error.html

@@ -0,0 +1,16 @@
+{% extends "base.html" %}
+{% block title %}Oops!{% endblock %}
+{% block head %}
+{{ super() }}
+{% endblock %}
+{% block content %}
+<div class="text-center">
+    <h1 class="text-2xl font-bold mb-4">Login failed.</h1>
+    <p class="mb-4">{{ error }}</p>
+    <div class="my-6">
+        <a href='/auth/oidc/redirect'
+            class="w-full py-2 px-4 bg-blue-500 text-white font-semibold rounded-lg shadow-md hover:bg-blue-700 focus:outline-none focus:ring-2 focus:ring-blue-400 focus:ring-opacity-75">Try
+            again</a>
+    </div>
+</div>
+{% endblock %}