chat: Fix create post without a topic

[AlaaElden98]

When the option 'require topics in stream messages' is checked,the user
shouldn't be able to post a message without a topic.

• Store the setting in RealmState
• Populate it in realmReducer
• Add a selector for it in directSelector
• Add the setting to ComposeBox props and connect call,and use it

Fixes: #4378

[chrisbobbe]

Thanks, @AlaaElden98! See a few small comments below.

Also, I think the commit message can be tightened up a bit:

chat: Fix create post without a topic

Why i did these changes?
-When the option 'require topics in stream messages' is checked,the user
shouldn't be able to post a message without a topic.

What changes:
* Store the setting in `RealmState`
* Populate it in `realmReducer`
* Add a selector for it in `directSelector`
* Add the setting to `ComposeBox` props and `connect` call,and use it
* Edit `realmReducer-test` to test the new changes

Fixes: #4378

• One thing is that the "What changes" list duplicates what's already clear by looking at the code changes, so I think that can just be removed. 🙂 The changes are pretty small, straightforward, and unsurprising.

• Let's give the summary line a bit more detail. How about something like, "ComposeBox: Prevent sending empty-topic messages if topics are mandatory."

• Then, the summary line plus the Fixes: line should pretty much answer the question of why the changes were made. So the "Why i did these changes?" section can disappear too, to leave us with the following:

  ComposeBox: Prevent sending empty-topic messages if topics are mandatory.
  
  Fixes: #4378
  

  That's shorter, and still gets the job done. 🙂

[chrisbobbe]

Let's add a dropCache migration in src/boot/store.js for this. Something like,

  // Add `isTopicMandatory` to `state.realm`.
  '27': dropCache,

[AlaaElden98]

That's new, I understand what this does, but when should I add a dropCache?

[AlaaElden98]

And i think you mean '28': dropCache ? there is already
'27': state => ({ ...state, accounts: state.accounts.filter(a => a.email !== ''), }),

[AlaaElden98]

@chrisbobbe, Thanks for the review, the PR is ready for another one.

[gnprice]

This issue was resolved by #4798. Thanks @AlaaElden98 for your work on this!