Event messages are treated case-sensitively based on topic in topic narrow

[sm-sayedi]

Steps to reproduce

• Open a topic narrow on the mobile app, e.g., #test here > Sayed.
• On Web, go to #test here, choose "sayed" (all lowercase) in the topic field, and leave a message.

Expected behavior

The new message should appear on the mobile app where the topic narrow for the topic "Sayed" is opened, because the topics "Sayed" and "sayed" should be treated the same.

Actual behavior

The new message doesn't appear on the mobile app.

[alya]

Adding to the current milestone, since it looks like this is being worked on.