[julia] fix regex escape on server codegen (#21009)

* [julia] fix regex escape on server codegen

Fixed escaping of regex patterns on julialang server codegen.

* add comment for the escapeRegex method

* simplify

Author: tanmaykm

Diff for: modules/openapi-generator/src/main/java/org/openapitools/codegen/languages/AbstractJuliaCodegen.java

@@ -454,29 +454,6 @@ public String escapeQuotationMark(String input) {
         return input.replace("\"", "\\\"");
     }
 
-    protected String escapeRegex(String pattern) {
-        pattern = pattern.replaceAll("\\\\\\\\", "\\\\");
-        pattern = pattern.replaceAll("^/", "");
-        pattern = pattern.replaceAll("/$", "");
-        return pattern;
-    }
-
-    /**
-     * Convert OpenAPI Parameter object to Codegen Parameter object
-     *
-     * @param imports set of imports for library/package/module
-     * @param param   OpenAPI parameter object
-     * @return Codegen Parameter object
-     */
-    @Override
-    public CodegenParameter fromParameter(Parameter param, Set<String> imports) {
-        CodegenParameter parameter = super.fromParameter(param, imports);
-        if (parameter.pattern != null) {
-            parameter.pattern = escapeRegex(parameter.pattern);
-        }
-        return parameter;
-    }
-
     /**
      * Convert OAS Property schema to Codegen Property object.
      * <p>
@@ -498,9 +475,6 @@ public CodegenProperty fromProperty(String name, Schema schema, boolean required
         if (needsVarEscape(property.name)) {
             property.name = "var\"" + property.name + "\"";
         }
-        if (property.pattern != null) {
-            property.pattern = escapeRegex(property.pattern);
-        }
         return property;
     }
 
@@ -531,6 +505,19 @@ private void changeParamNames(List<CodegenParameter> paramsList, HashSet<String>
         }
     }
 
+    @Override
+    public String toRegularExpression(String pattern) {
+        if (pattern == null) {
+            return pattern;
+        }
+
+        pattern = escapeText(pattern);
+        // escapeText unnecessarily escapes `\` such that `\.` in the regex ends up as `\\.` for example.
+        // we need to restore it back by converting `\\` to `\`
+        pattern = pattern.replaceAll("\\\\\\\\", "\\\\");
+        return pattern;
+    }
+
     /**
      * Convert OAS Operation object to Codegen Operation object
      *