[feature]: More Descriptive Error on Attempted Spend from Reserve

[levmi]

Is your feature request related to a problem? Please describe.
I've heard from developers that users get frustrated when they're onboarding to Lightning, set up a channel, then try to spend the an amount below the reserve threshold of that channel, but run into the channel reserve requirement. When they try to spend the full amount, the error returns as insufficient balance. The developer who flagged this actually believes that it could be impacting initial Lightning usage as people try Lightning out, it fails and they just move on.

Describe the solution you'd like
It would be nice to have a more descriptive error here like Cannot Spend due to Channel Reserve or something along those lines. This would allow for developers to give more context to end users about what went wrong and better educate them on how to use Lightning.

Additional context
Comes from the Voltage team

[ziggie1984]

I think this relates to #8817, which would be even better to give devs the exact amount they can send on that channel.