Fix permissions check for inviting users to a service

This changeset reverts a change we had made previously where we accidentally locked down the ability for service admins to invite other users to their own service.  This removes the platform admin user check and reverts it back to the proper permissions check (including adjusting the tests to account for this).

Signed-off-by: Carlo Costino <carlo.costino@gsa.gov>

tests/app/main/views/test_manage_users.py

@@ -800,10 +800,13 @@ def test_should_show_page_for_inviting_user_with_email_prefilled(
         user_id=fake_uuid,
         # We have the user’s name in the H1 but don’t want it duplicated
         # in the page title
-        _test_page_title=False,
-        _expected_status=403,
+        _test_page_title=False
     )
-    assert "not allowed to see this page" in page.h1.string.strip()
+    assert normalize_spaces(page.select_one("title").text).startswith(
+        "Invite a team member"
+    )
+    assert normalize_spaces(page.select_one("h1").text) == ("Invite Service Two User")
+    assert not page.select("input#email_address") or page.select("input[type=email]")
 
 
 def test_should_show_page_if_prefilled_user_is_already_a_team_member(
@@ -1280,9 +1283,11 @@ def test_user_cant_invite_themselves(
             "permissions_field": ["send_messages", "manage_service", "manage_api_keys"],
         },
         _follow_redirects=True,
-        _expected_status=403,
+        _expected_status=200,
     )
-    assert "not allowed to see this page" in page.h1.string.strip()
+    assert page.h1.string.strip() == "Invite a team member"
+    form_error = page.find("span", class_="usa-error-message").text.strip()
+    assert form_error == "Error: You cannot send an invitation to yourself"
     assert not mock_create_invite.called