[Feature]: Add a 'comment' field for Transfer transactions

[stefashkaa]

As a

user

I want to

make transfers with additional info (like detailed invoices or links to that info or any other info)

So that

I can use transfers for payments

Preconditions

1. Add new field for Transfer extrinsic
2. Add new property for Transfer events
3. Set a limit of the length of 'comment' field
4. Check backward compatibility of indexers during the new property in the event
5. Implement this logic for each client (Polkaswap/SORA mobile/Fearless)
6. Check extrinsic weights

Flow

No response

Postconditions

No response