Offline Downloads: Add notice when max no. of documents is reached

[rittermo]

We should notify the user when the max no. of files that can be attached to the offline phase is reached. If the limit is reached, there should be a notice that reads “The maximum number of files that can be uploaded is reached. Please delete one of the existing files first to upload a new file.”

[MagdaN]

@damusp can you consider this, when preparing the designs.

[MagdaN]

@damusp how could that be displayed? Could you update the designs?

[SabineJulia]

@damusp please tell what you think?

[damusp]

Sorry, I've lost track of this one. Thanks for reminding me @SabineJulia. I will get back to you guys!