fix: [CN-69] respect struct json tags in JSON encoder with UseJSONTagName enabled

[vpakhuchyi]

Pull request

Link to the related ticket

https://censor.atlassian.net/browse/CN-69

Description of changes

When UseJSONTagName configuration option is enabled JSON encoder shall use json structure tags instead of field names.

Checklist

Please ensure that your pull request complies with the following requirements:

• The changes have been tested locally (if applicable).
• The documentation has been updated (if applicable).

[Copilot]

Pull Request Overview

This PR implements support for the UseJSONTagName configuration option in the JSON encoder, allowing struct fields to use their json tag names instead of Go field names when encoding.

• Adds logic to parse and respect json struct tags in the JSON encoder
• Implements proper handling of tag options, dash tags (json:"-"), and fallback to field names
• Updates documentation to clearly explain the feature behavior

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
internal/encoder/json_encoder.go	Implements JSON tag parsing logic in getStructFields method, adds UseJSONTagName configuration to encoder initialization, includes gocognit suppression for increased complexity
internal/encoder/json_encoder_test.go	Adds comprehensive test coverage for UseJSONTagName feature with multiple edge cases including aliased tags, skipped fields, empty tag names, and default behavior
docs/index.md	Updates configuration documentation to accurately describe the UseJSONTagName option behavior, clarifying how it mirrors Go's encoding/json package

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