[proxy] Propagate more console API errors to the user

This patch aims to fix some of the inconsistencies in error reporting,
for example "Internal error" or "Console request failed" instead of
"password authentication failed for user '<NAME>'".

proxy/src/proxy/tests.rs

@@ -1,6 +1,6 @@
 ///! A group of high-level tests for connection establishing logic and auth.
 use super::*;
-use crate::{auth, scram};
+use crate::{auth, sasl, scram};
 use async_trait::async_trait;
 use rstest::rstest;
 use tokio_postgres::config::SslMode;
@@ -100,8 +100,7 @@ impl Scram {
     }
 
     fn mock(user: &str) -> Self {
-        let salt = rand::random::<[u8; 32]>();
-        Scram(scram::ServerSecret::mock(user, &salt))
+        Scram(scram::ServerSecret::mock(user, rand::random()))
     }
 }
 
@@ -111,13 +110,17 @@ impl TestAuth for Scram {
         self,
         stream: &mut PqStream<Stream<S>>,
     ) -> anyhow::Result<()> {
-        auth::AuthFlow::new(stream)
+        let outcome = auth::AuthFlow::new(stream)
             .begin(auth::Scram(&self.0))
             .await?
             .authenticate()
             .await?;
 
-        Ok(())
+        use sasl::Outcome::*;
+        match outcome {
+            Success(_) => Ok(()),
+            Failure(reason) => bail!("autentication failed with an error: {reason}"),
+        }
     }
 }