minor refactoring and fixes: dev module

[AnthonyMichaelTDM]

4 commits, details as follows:

• fix(dev): don't panic in is_connected if we couldn't get a connection to the db

it doesn't make sense for a failed connection to panic in a function that's supposed to check for a connection, this fixes that (probably) unintended behavior.

• perf: assigning the result of Clone::clone() may be inefficient

https://rust-lang.github.io/rust-clippy/master/index.html#/assigning_clones using clone_from let's us avoid unnecessary allocations

• refactor(dev): migrate_db fn to return result instead of ( success, optional error_message ) tuple.

We aren't in Go, we have better error handling available so should take advantage of it

TODO: There are more cases in this function where it may be better to propagate errors rather than panicing

• refactor(dev): listen_for_signals, rename variables and refactor error handling

https://rust-lang.github.io/rust-clippy/master/index.html#/never_loop

the loop only actually runs once, so an if let is a much more clear expression.