Fix: Add missing type annotations to serialization dataclass fields

[rraulinio]

Relates to: minio/mint#399.

Problem

PR #1504 (v7.2.17) converted serialization classes to dataclasses but did not add type annotations to fields. Without type annotations, they don't become __init__ parameters.

Error:

CSVInputSerialization(file_header_info=FILE_HEADER_INFO_NONE)
# TypeError: __init__() got an unexpected keyword argument 'file_header_info'

Root Cause
# Broken (v7.2.17+):

@dataclass(frozen=True)
class CSVInputSerialization(InputSerialization):
    file_header_info = None 

# Fixed:

@dataclass(frozen=True)
class CSVInputSerialization(InputSerialization):
    file_header_info: Optional[str] = None

# Solution:
Add Optional[str] type annotations to all dataclass fields in:

• CSVInputSerialization(7 fields)
• JSONInputSerialization (1 field)
• CSVOutputSerialization (5 fields)
• JSONOutputSerialization (1 field)

[Copilot]

Pull Request Overview

This PR fixes a critical bug introduced in v7.2.17 where serialization dataclass fields were missing type annotations, preventing them from being used as __init__ parameters and causing TypeError when instantiating these classes with arguments.

• Added Optional[str] type annotations to 14 dataclass fields across 4 serialization classes
• Enables proper instantiation of serialization classes with keyword arguments (e.g., CSVInputSerialization(file_header_info=FILE_HEADER_INFO_NONE))
• No functional changes to existing logic or validation

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[rraulinio]

Blocking minio/mint#399.