Add sample spec to catch external file reference issues in swagger-pa…

…rser (#17773)

* add a sample that catches swagger-parser issues with external refs

* generate samples for new test spec

bin/configs/go-echo-external-refs-test.yaml

@@ -0,0 +1,6 @@
+generatorName: go
+outputDir: samples/client/echo_api/go-external-refs
+inputSpec: modules/openapi-generator/src/test/resources/3_0/external-refs/echo_api.yaml
+templateDir: modules/openapi-generator/src/main/resources/go
+additionalProperties:
+  hideGenerationTimestamp: "true"

modules/openapi-generator/src/test/resources/3_0/external-refs/components/paths/string.yaml

@@ -0,0 +1,46 @@
+get:
+  description: Test path parameter(s)
+  operationId: "tests/path/string/{path_string}/integer/{path_integer}/{enum_nonref_string_path}/{enum_ref_string_path}"
+  parameters:
+    - explode: false
+      in: path
+      name: path_string
+      required: true
+      schema:
+        type: string
+      style: simple
+    - explode: false
+      in: path
+      name: path_integer
+      required: true
+      schema:
+        type: integer
+      style: simple
+    - explode: false
+      in: path
+      name: enum_nonref_string_path
+      required: true
+      schema:
+        enum:
+          - success
+          - failure
+          - unclassified
+        type: string
+      style: simple
+    - explode: false
+      in: path
+      name: enum_ref_string_path
+      required: true
+      schema:
+        $ref: "../schemas/StringEnumRef.yaml"
+      style: simple
+  responses:
+    "200":
+      content:
+        text/plain:
+          schema:
+            type: string
+      description: Successful operation
+  summary: Test path parameter(s)
+  tags:
+    - path

modules/openapi-generator/src/test/resources/3_0/external-refs/components/schemas/StringEnumRef.yaml

@@ -0,0 +1,5 @@
+type: string
+enum:
+  - success
+  - failure
+  - unclassified