Add URLs to download the agreement without login

So that we can share these URLs in an email we’re sending out.

app/main/views/agreement.py

@@ -1,4 +1,4 @@
-from flask import render_template, send_file
+from flask import abort, render_template, request, send_file, url_for
 from flask_login import login_required
 
 from app.main import main
@@ -28,3 +28,24 @@ def download_agreement():
     return send_file(**get_mou(
         AgreementInfo.from_current_user().crown_status_or_404
     ))
+
+
+@main.route('/agreement/<variant>', endpoint='public_agreement')
+@main.route('/agreement/<variant>.pdf', endpoint='public_download_agreement')
+def public_agreement(variant):
+
+    if variant not in {'crown', 'non-crown'}:
+        abort(404)
+
+    if request.endpoint == 'main.public_download_agreement':
+        return send_file(**get_mou(
+            organisation_is_crown=(variant == 'crown')
+        ))
+
+    agreement_info = AgreementInfo.from_current_user()
+
+    return render_template(
+        'views/agreement-public.html',
+        owner=agreement_info.owner,
+        download_link=url_for('.public_download_agreement', variant=variant),
+    )