Fix validation errors overwriting each other

Validation errors were stored by object ID, which made no sense. It
wasn't necessary, but provided the possibility of a validation error
overwriting a previous one that applied to the same object.

On top of that, this change is a simplification, so a win all around.

crates/fj-core/src/layers/validation.rs

@@ -60,7 +60,7 @@ impl Command<Validation> for TakeErrors {
         state: &Validation,
         events: &mut Vec<Self::Event>,
     ) -> Self::Result {
-        let errors = ValidationErrors(state.errors.values().cloned().collect());
+        let errors = ValidationErrors(state.errors.to_vec());
 
         events.push(self);
 
@@ -92,6 +92,6 @@ pub struct ValidationFailed {
 
 impl Event<Validation> for ValidationFailed {
     fn evolve(&self, state: &mut Validation) {
-        state.errors.insert(self.object.id(), self.err.clone());
+        state.errors.push(self.err.clone());
     }
 }

crates/fj-core/src/validation/validation.rs

@@ -1,6 +1,4 @@
-use std::{collections::HashMap, error::Error, thread};
-
-use crate::storage::ObjectId;
+use std::{error::Error, thread};
 
 use super::{ValidationConfig, ValidationError};
 
@@ -8,7 +6,7 @@ use super::{ValidationConfig, ValidationError};
 #[derive(Default)]
 pub struct Validation {
     /// All unhandled validation errors
-    pub errors: HashMap<ObjectId, ValidationError>,
+    pub errors: Vec<ValidationError>,
 
     /// Validation configuration for the validation service
     pub config: ValidationConfig,
@@ -17,7 +15,7 @@ pub struct Validation {
 impl Validation {
     /// Construct an instance of `Validation`, using the provided configuration
     pub fn with_validation_config(config: ValidationConfig) -> Self {
-        let errors = HashMap::new();
+        let errors = Vec::new();
         Self { errors, config }
     }
 }
@@ -31,7 +29,7 @@ impl Drop for Validation {
                 errors:"
             );
 
-            for err in self.errors.values() {
+            for err in self.errors.iter() {
                 println!("{}", err);
 
                 // Once `Report` is stable, we can replace this: