ref(cells): Organization invites go the correct org scoped routes

[lynnagara]

Updates get_invite_link to generate org-scoped invite URLs (/accept/<org_slug>/<member_id>//) instead of the legacy no-org format (/accept/<member_id>//).

This is a prerequisite for removing the legacy no-org invite route and ensuring this works even when multiple cells are configured.

[github-actions]

Backend Test Failures

Failures on bac4c3e in this run:

tests/sentry/core/endpoints/test_organization_details.py::OrganizationSettings2FATest::test_owner_can_set_org_2fa — log

[gw0] linux -- Python 3.13.1 /home/runner/work/sentry/sentry/.venv/bin/python3
tests/sentry/core/endpoints/test_organization_details.py:2330: in test_owner_can_set_org_2fa
    self.assert_2fa_email_equal(mail.outbox, user_emails_without_2fa)
tests/sentry/core/endpoints/test_organization_details.py:2227: in assert_2fa_email_equal
    assert invite_url_regex.search(email.body), (
E   AssertionError: No invite URL found in 2FA invite email body to: ['foo_5@example.com']
E   assert None
E    +  where None = <built-in method search of re.Pattern object at 0x7fd9d87bdd40>('Setup Two-Factor Authentication\n\nThe Rapid Narwhal organization now requires all members to enable\ntwo-factor auth...ings:\nhttp://example.com/accept/rapid-narwhal/190/a1c1559ab7b90eeea67dd639e43705dfded50b2fb96163d9cc91382860960169/\n')
E    +    where <built-in method search of re.Pattern object at 0x7fd9d87bdd40> = re.compile('http://.*/accept/[0-9]+/[a-f0-9]+/').search
E    +    and   'Setup Two-Factor Authentication\n\nThe Rapid Narwhal organization now requires all members to enable\ntwo-factor auth...ings:\nhttp://example.com/accept/rapid-narwhal/190/a1c1559ab7b90eeea67dd639e43705dfded50b2fb96163d9cc91382860960169/\n' = <django.core.mail.message.EmailMultiAlternatives object at 0x7fd9ce262c50>.body

tests/sentry/core/endpoints/test_organization_details.py::OrganizationSettings2FATest::test_manager_can_set_2fa — log

[gw1] linux -- Python 3.13.1 /home/runner/work/sentry/sentry/.venv/bin/python3
tests/sentry/core/endpoints/test_organization_details.py:2311: in test_manager_can_set_2fa
    self.assert_2fa_email_equal(mail.outbox, [self.owner.email])
tests/sentry/core/endpoints/test_organization_details.py:2227: in assert_2fa_email_equal
    assert invite_url_regex.search(email.body), (
E   AssertionError: No invite URL found in 2FA invite email body to: ['2aa15ad15f3c4ca9b3491cbae3b316b7@example.com']
E   assert None
E    +  where None = <built-in method search of re.Pattern object at 0x7f39807e45b0>('Setup Two-Factor Authentication\n\nThe Healthy Cat organization now requires all members to enable\ntwo-factor authen...ttings:\nhttp://example.com/accept/healthy-cat/114/39a6c4e79fdc86ac63dc4b88bfece458855ed581563a75fd45162cd801a8b994/\n')
E    +    where <built-in method search of re.Pattern object at 0x7f39807e45b0> = re.compile('http://.*/accept/[0-9]+/[a-f0-9]+/').search
E    +    and   'Setup Two-Factor Authentication\n\nThe Healthy Cat organization now requires all members to enable\ntwo-factor authen...ttings:\nhttp://example.com/accept/healthy-cat/114/39a6c4e79fdc86ac63dc4b88bfece458855ed581563a75fd45162cd801a8b994/\n' = <django.core.mail.message.EmailMultiAlternatives object at 0x7f397bac4aa0>.body

[markstory]

Looks good, but we'll need to do more changes to completely remove sentry-accept-invite.