Fix code issues to make main compile again

[SwishSwushPow]

📇 Description

Hi everyone 👋 I was looking at supercluster because the dependencies resolved a bit awkwardly in our own project, so I wanted to build it locally and see if I could tweak things. I noticed that checking out the main branch left me with a state I couldn't compile, so I started to fix these issues.

The bump for the Rust version to 1.88.0 is required to be able to build the geojson dependency I think. Otherwise we get the following error:

error[E0658]: `let` expressions in this position are unstable
  --> /Users/bjoern/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/geojson-1.0.0/src/util.rs:19:8
   |
19 |     if let Some(some_fm) = fm
   |        ^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information

For more information about this error, try `rustc --explain E0658`.

🚨 Checklist

• My changes do not introduce backwards compatibility issues.
• I have commented my code, particularly in hard-to-understand areas.
• I have actively considered and searched for potential security issues and did address these.

🧪 Tests

• I have added missing tests for related code.
• I have manually tested my code for regression on existing functionality.
• I have added tests that prove my fix is effective or that my feature works.

There are still issues with tests I think, but I have not yet fixed them because I haven't had the time to figure out what is going on there or if I'm just running them incorrectly. 😅