refactor(config): simplify config reading

!squash me

!squash me

derive_macro/src/from_file.rs

@@ -0,0 +1,42 @@
+use proc_macro::TokenStream;
+use quote::quote;
+use syn::{Data, DeriveInput, Fields, Ident};
+
+pub fn impl_from_file(input: DeriveInput) -> TokenStream {
+    let name = &input.ident;
+    let file_name = format!("{name}File");
+    let file_ident = Ident::new(&file_name, name.span());
+
+    let fields = match &input.data {
+        Data::Struct(data) => match &data.fields {
+            Fields::Named(fields) => &fields.named,
+            _ => panic!("Only named fields are supported"),
+        },
+        _ => panic!("Only structs are supported"),
+    };
+
+    let field_idents = fields.iter().map(|f| &f.ident);
+    let field_idents2 = field_idents.clone();
+
+    quote! {
+        impl #name {
+            fn from_file(file: Option<#file_ident>) -> Self 
+            where
+                #file_ident: Default + Clone
+            {
+                let default = #file_ident::default();
+                let file = file.unwrap_or_else(|| default.clone());
+
+                Self {
+                    #(#field_idents: file.#field_idents2.unwrap_or_else(|| default.#field_idents.clone().unwrap())),*
+                }
+            }
+        }
+
+        impl From<Option<#file_ident>> for #name {
+            fn from(value: Option<#file_ident>) -> Self {
+                Self::from_file(value)
+            }
+        }
+    }.into()
+}

derive_macro/src/lib.rs

@@ -0,0 +1,10 @@
+mod from_file;
+
+use proc_macro::TokenStream;
+use syn::{DeriveInput, parse_macro_input};
+
+#[proc_macro_derive(FromFile)]
+pub fn derive_from_file(input: TokenStream) -> TokenStream {
+    let input = parse_macro_input!(input as DeriveInput);
+    from_file::impl_from_file(input)
+}