Allow encryption for all decryption groups #30
Description
Currently, using decryption tasks is a bit strange - one encrypts a message for a group that he is part of as well. More realistic scenario is encrypting a message to a group, where the sender is not a member, i.e., sending an encrypted message to someone else.
AFAIK, the server allows listing all groups, now. Thus, I suggest to list all existing decryption groups (this feature is not relevant for other groups), even those the client device is not a member of. It should be then possible to send an encrypted message to any of the listed groups.
It's up to consideration, how to make it visible to the user, which groups he is(n't) part of. One option is to order them. Or have two tabs (My groups, Other) or something along these lines.
Afterwards, we can rethink the group creation and management, it would make sense to add visibility tag, which would allow/forbid sharing the group to others.
Overall, there may be some nuances I haven't thought of, so please create this as a PR and let's test it first before merging.