add a system prompt snapshot test (#5305)

Cargo.lock

@@ -2608,6 +2608,7 @@ dependencies = [
  "futures",
  "include_dir",
  "indoc",
+ "insta",
  "jsonschema",
  "jsonwebtoken",
  "keyring",
@@ -3518,6 +3519,17 @@ dependencies = [
  "generic-array",
 ]
 
+[[package]]
+name = "insta"
+version = "1.43.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "46fdb647ebde000f43b5b53f773c30cf9b0cb4300453208713fa38b2c70935a0"
+dependencies = [
+ "console",
+ "once_cell",
+ "similar",
+]
+
 [[package]]
 name = "interpolate_name"
 version = "0.2.4"