fix: clarify config parse errors (#2360)

* fix: improve config parse diagnostics
* fix: polish config error context
* test: cover non-ascii config diagnostics

Cargo.lock

@@ -241,6 +241,16 @@ dependencies = [
  "password-hash",
 ]
 
+[[package]]
+name = "ariadne"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "36f5e3dca4e09a6f340a61a0e9c7b61e030c69fc27bf29d73218f7e5e3b7638f"
+dependencies = [
+ "unicode-width 0.1.11",
+ "yansi",
+]
+
 [[package]]
 name = "arrayvec"
 version = "0.7.6"
@@ -2234,6 +2244,7 @@ dependencies = [
  "aes-gcm",
  "anyhow",
  "arc-swap",
+ "ariadne",
  "async-recursion",
  "async-ringbuf",
  "async-stream",