fix: over regex surrounding (by copilot code review)

Signed-off-by: Sebastian Gaviria Tangarife <sgt.911@outlook.com>

Author: SGT911

pkg/regexp/regexp.go

@@ -74,3 +74,7 @@ func HasArbitraryWildcard(pattern string) (bool, error) {
 
 	return inspectForWildcardSegments(ast), nil
 }
+
+func SurroundRedirectURIRegexp(uri string) string {
+	return `\A(?:` + uri + `)\z`
+}

server/authflow/request.go

@@ -146,7 +146,7 @@ func validateRegexpRedirectURI(redirectURIs []string, redirectURI string, allowW
 			continue
 		}
 
-		rgx, err := regexp.Compile(surroundRedirectURIRegexp(uri))
+		rgx, err := regexp.Compile(dexRegexp.SurroundRedirectURIRegexp(uri))
 		if err != nil {
 			continue
 		}
@@ -159,19 +159,6 @@ func validateRegexpRedirectURI(redirectURIs []string, redirectURI string, allowW
 	return false
 }
 
-func surroundRedirectURIRegexp(uri string) (result string) {
-	result = uri
-	if result[0] != '^' {
-		result = "^" + result
-	}
-
-	if result[len(result)-1] != '$' {
-		result = result + "$"
-	}
-
-	return
-}
-
 func validateConnectorID(connectors []storage.Connector, connectorID string) bool {
 	for _, c := range connectors {
 		if c.ID == connectorID {