Improve error handling (#33)

* refactor: improve error handling

* fix: specify bind address instead of port

* fix: remove temporary testing file

* fix(errors): change error names to snake_case

* refactor(errors): split indexing error types, remove unused errors

* feat: add env variable checking at program start

This just checks whether the enviroment variables exist and can
parse to the given type and gives a warning if they can't. This
should prevent cases where the program fails at runtime due to
checking an environment variable that doesn't exist.

src/models/ids.rs

@@ -60,7 +60,7 @@ pub struct Base62Id(pub u64);
 #[derive(Error, Debug)]
 pub enum DecodingError {
     /// Encountered a non base62 character in base62 string
-    #[error("Invalid character `{0:?}` in base62 encoding")]
+    #[error("Invalid character {0:?} in base62 encoding")]
     InvalidBase62(char),
     /// Encountered integer overflow when decoding a base62 id.
     #[error("Base62 decoding overflowed")]