Add support for OpenAPI Generator import-mappings property

This allows users to specify custom import mappings for generated code,
enabling control over which classes are imported for specific types.

Author: bu3

internal/openapi_generator.bzl

@@ -43,6 +43,10 @@ def _new_generator_command(ctx, declared_dir, rjars):
         mappings = _comma_separated_pairs(ctx.attr.type_mappings),
     )
 
+    gen_cmd += ' --import-mappings "{mappings}"'.format(
+        mappings = _comma_separated_pairs(ctx.attr.import_mappings),
+    )
+
     gen_cmd += ' --reserved-words-mappings "{reserved_words_mappings}"'.format(
         reserved_words_mappings = ",".join(ctx.attr.reserved_words_mappings),
     )
@@ -166,6 +170,7 @@ _openapi_generator = rule(
         "system_properties": attr.string_dict(),
         "engine": attr.string(),
         "type_mappings": attr.string_dict(),
+        "import_mappings": attr.string_dict(),
         "reserved_words_mappings": attr.string_list(),
         "is_windows": attr.bool(mandatory = True),
         "_jdk": attr.label(

internal/test/basic/BUILD.bazel

@@ -64,3 +64,13 @@ openapi_generator(
     spec = "petstore.yaml",
     template_dir = "python-templates"
 )
+
+openapi_generator(
+    name = "petstore_java_import_mappings",
+    generator = "java",
+    spec = "petstore.yaml",
+    import_mappings = {
+        "Date": "java.time.LocalDate",
+        "DateTime": "java.time.OffsetDateTime",
+    },
+)