Increase invoice expiration

[reneaaron]

We see quite some errors in our logs that arise from expired invoices being paid. While those cases are rare (compared to the total number of transactions), they are a nightmare for users:

• They created an invoice and sent it to a friend via DM
• Their friend wanted to pay the next day but received an error during the payment
• Now they have to start over again: create a fresh invoice, send it to them (and remind them to pay within 24 hours)

From a user perspective I would argue that it isn't very understandable that an invoice expires at all.

Raising this default expiration limit won't solve the problem fundamentally, nevertheless I think it would still be an improvement for quite a lot of the cases:

Telling from our logs approximately 95% of the errors would disappear if we raise the limit to one week.

[bumi]

why? I would rather reduce it.

[reneaaron]

Updated the issue description and added some quick analysis about the impact from our error logs.