Add MaxFileSizeValidator and MinFileSizeValidator for file size constraints

[mahdirahimi1999]

Add file size validators for FileField and ImageField

Adds two new validators to enforce file size constraints on uploaded files:

Background

In many of our DRF and Django projects, we work extensively with FileField and ImageField and need to validate file sizes. I've been creating these validators locally, and other developers have been implementing similar solutions. I thought it would be beneficial to create a standardized class that can be added to DRF and used across our projects.

New Validators

• MaxFileSizeValidator: Ensures files don't exceed a maximum size (in bytes)
• MinFileSizeValidator: Ensures files meet a minimum size (in bytes)

Features

• Customizable error messages and codes
• Deconstructible for migrations
• Works with FileField and ImageField
• Gracefully handles objects without .size attribute

Usage

from rest_framework.validators import MaxFileSizeValidator, MinFileSizeValidator

class FileUploadSerializer(serializers.Serializer):
    file = serializers.FileField(validators=[
        MaxFileSizeValidator(1024 * 1024),  # 1MB max
        MinFileSizeValidator(1024),         # 1KB min
    ])

Implementation

• Added to rest_framework/validators.py
• 77 new tests covering unit and integration scenarios
• Documentation added to docs/api-guide/validators.md
• All existing tests pass (1577 total)

Error Codes

• max_file_size - Default for MaxFileSizeValidator
• min_file_size - Default for MinFileSizeValidator