Compile regex when parsing config

The regexes are now compiled when the config is parsed and not each
time a new webhook is received.

Adapt tests to using parsed regex.

Cargo.lock

@@ -1301,6 +1301,16 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "serde_regex"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a8136f1a4ea815d7eac4101cfd0b16dc0cb5e1fe1b8609dfd728058656b7badf"
+dependencies = [
+ "regex",
+ "serde",
+]
+
 [[package]]
 name = "serde_yaml"
 version = "0.8.21"
@@ -1931,6 +1941,7 @@ dependencies = [
  "run_script",
  "serde",
  "serde_json",
+ "serde_regex",
  "serde_yaml",
  "sha2",
  "thiserror",