Unclear message when sharing search links with a non-shared context

Created by: benvenker

[Slack post](https://sourcegraph.slack.com/archives/C03CSAER9LK/p1656009530554419}

The experience when sending a link is pretty clunky when you use a context - by default the context gets embedded in the URL but when you share it with someone without access to that context, you get an error that gives no indication that the context is the issue: https://sourcegraph.slack.com/archives/C02MWRMAFR8/p1656007607201609?thread_ts=1656006376.275619&cid=C02MWRMAFR8 Example link: https://sourcegraph.com/search?q=context:@sourcegraph/all+repo:sourcegraph+dev/ci/.*.sh+select:content&patternType=regexp