billing/sponsorship: Allow blank organization URLs.

We ran into a bug in production caused by two issues:
- Some users came from orgs that didn't have a website and since
  the URL field was required, they submitted invalid URLs.
- We didn't properly respond to invalid form submissions, which
  led to UnboundLocalError exceptions in another part of the
  code.

This commit solves this by doing the following:
- We now allow blank URLs and have a convenient placeholder text
  label that tells users that they may leave the URL field blank.
- This commit refactors the code such that invalid form submissions
  result in an informative error message about what exactly went
  wrong.

corporate/migrations/0013_alter_zulipsponsorshiprequest_org_website.py

@@ -0,0 +1,18 @@
+# Generated by Django 3.2.5 on 2021-08-06 19:18
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("corporate", "0012_zulipsponsorshiprequest"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="zulipsponsorshiprequest",
+            name="org_website",
+            field=models.URLField(blank=True, null=True),
+        ),
+    ]

corporate/models.py

@@ -204,6 +204,6 @@ class ZulipSponsorshipRequest(models.Model):
     )
 
     MAX_ORG_URL_LENGTH: int = 200
-    org_website: str = models.URLField(max_length=MAX_ORG_URL_LENGTH)
+    org_website: str = models.URLField(max_length=MAX_ORG_URL_LENGTH, blank=True, null=True)
 
     org_description: str = models.TextField(default="")

corporate/tests/test_stripe.py

@@ -1461,6 +1461,32 @@ class StripeTest(StripeTestCase):
             orjson.loads(response.content)["error_description"], "uncaught exception during upgrade"
         )
 
+    def test_request_sponsorship_form_with_invalid_url(self) -> None:
+        user = self.example_user("hamlet")
+        self.login_user(user)
+        data = {
+            "organization-type": Realm.ORG_TYPES["opensource"]["id"],
+            "website": "invalid-url",
+            "description": "Infinispan is a distributed in-memory key/value data store with optional schema.",
+        }
+
+        response = self.client_post("/json/billing/sponsorship", data)
+
+        self.assert_json_error(response, "Enter a valid URL.")
+
+    def test_request_sponsorship_form_with_blank_url(self) -> None:
+        user = self.example_user("hamlet")
+        self.login_user(user)
+        data = {
+            "organization-type": Realm.ORG_TYPES["opensource"]["id"],
+            "website": "",
+            "description": "Infinispan is a distributed in-memory key/value data store with optional schema.",
+        }
+
+        response = self.client_post("/json/billing/sponsorship", data)
+
+        self.assert_json_success(response)
+
     def test_request_sponsorship(self) -> None:
         user = self.example_user("hamlet")
         self.assertIsNone(get_customer_by_realm(user.realm))

corporate/views/upgrade.py

@@ -203,7 +203,7 @@ def initial_upgrade(
 
 
 class SponsorshipRequestForm(forms.Form):
-    website = forms.URLField(max_length=ZulipSponsorshipRequest.MAX_ORG_URL_LENGTH)
+    website = forms.URLField(max_length=ZulipSponsorshipRequest.MAX_ORG_URL_LENGTH, required=False)
     organization_type = forms.IntegerField()
     description = forms.CharField(widget=forms.Textarea)
 
@@ -235,8 +235,8 @@ def sponsorship(
     post_data.update(organization_type=organization_type)
     form = SponsorshipRequestForm(post_data)
 
-    with transaction.atomic():
     if form.is_valid():
+        with transaction.atomic():
             sponsorship_request = ZulipSponsorshipRequest(
                 realm=realm,
                 requested_by=user,
@@ -275,3 +275,10 @@ def sponsorship(
         )
 
         return json_success()
+    else:
+        messages = []
+        for error_list in form.errors.get_json_data().values():
+            for error in error_list:
+                messages.append(error["message"])
+        message = " ".join(messages)
+        raise BillingError("Form validation error", message=message)

templates/corporate/upgrade.html

@@ -238,7 +238,7 @@
                                 <label>
                                     <h4>Organization website</h4>
                                 </label>
-                                <input name="website" style="width: 100%;" type="text" class="input-large" required/>
+                                <input name="website" style="width: 100%;" type="text" class="input-large" placeholder="{{ _('Leave blank if your organization does not have a website.') }}"/>
                                 <label>
                                     <h4>Describe your organization briefly</h4>
                                 </label>