Define the rules for data validation

[KubaMikolajczyk]

We have to define how we will treat data validation:

• input mandatory / optional?
• real time validation?
• define input behaviour

[KubaMikolajczyk]

Define how to show that avatar/cover image is required to proceed creating a channel - eventually rethink the process.

[kdembler]

just FYI, we currently don't require avatar and cover images