Increased test coverage and remove low-severity compiler warnings

[0xCooki]

TLDR: Increased test coverage, and removed all low-severity compiler warnings.

GM GM

My name is William Ridge (a.k.a Cooki), and if I may be so bold, I have some minor amendments to this Starport repo for your consideration.

Increased Test Coverage

This pull request increases test coverage for src/Custodian.sol and src/Starport.sol respectively to 100% for Lines, Statements, and Functions. Branches remain only partially covered; however I believe this results from a quirk of Foundry, moreso than a fault of the testing suite, although I may be mistaken about this (consult here for more information)

Before

After

Removed All Low-Severity Compiler Warnings

This pull request also removes many low-severity compiler warnings including: Warning (2072): Unused local variable, Warning (5667): Unused function parameter, Warning (2519): This declaration shadows an existing declaration, Warning (3420): Source file does not specify required compiler version, and Warning (1878): SPDX license identifier not provided in source file. Wherever possible I have attempted to keep as much of the original code untouched as possible, while also addressing these warnings. Stylistically, the modifications to src/Custodian.sol were inspired by this suggestion.

Thank You

Finally, thank you for your time! I very much appreciate the Astaria product, and it was a pleasure to work on this repo. If there are aspects of this pull request you are unhappy with please don't hesitate to let me know, and I will seek to address them.

Moreover, if there is any more ongoing work available that I might contribute to, please consider me for such a role, I would very much like to be an active contributor if possible. Thank you again.