refactor: add support for extending file storage to other schemes and provide a runtime flag for the same

[Chethan-rao]

Type of Change

• Bugfix
• New feature
• Enhancement
• Refactoring
• Dependency updates
• Documentation
• CI/CD

Description

This PR includes refactoring for:

• Enabling easy extension of other file storage schemes.
• Providing a runtime flag for the file storage feature.
• Restrict the file storage objects(structs, methods) visibility wherever possible.

Additional Changes

• This PR modifies the API contract
• This PR modifies the database schema
• This PR modifies application configuration/environment variables

Motivation and Context

Closes #3338, Closes #3347

How did you test it?

• Create a dispute and get the dispute_id

File System

1. File uploading

curl --location --request POST 'localhost:8080/files' \
--header 'Accept: application/json' \
--header 'api-key: dev_vbE0ODzAkDHFkW2FFQZEAU4VeSk5ij4kWOZl2JXqRtYf50rVqxefvSofYCqre89Q' \
--header 'Content-Type: multipart/form-data; boundary=6467930559a8e09e-babf866111649afb-06f42165ce9a45a7-bc825186544537e1' \
--header 'Accept-Encoding: gzip' \
--form 'purpose="dispute_evidence"' \
--form 'file=@"/Users/sai.harsha/Desktop/dummy.pdf"' \
--form 'dispute_id="dp_Hv9m2MJGRjptYmEYPqFa"'

2. File retrieve

curl --location --request GET 'localhost:8080/files/file_qXP0X6uAgLwSvswj8T41' \
--header 'Accept: application/json' \
--header 'api-key: dev_H3Uf7cssLge9XnWZZfV2M5xwqroMHt46cXh0EwXJQHTdYuBTVC3KVnA5Fo45hagw'

3. File delete

curl --location --request DELETE 'localhost:8080/files/file_z4giuhfczJqbXwNhazqS' \
--header 'Accept: application/json' \
--header 'api-key: dev_vbE0ODzAkDHFkW2FFQZEAU4VeSk5ij4kWOZl2JXqRtYf50rVqxefvSofYCqre89Q'

Aws S3

1. File uploading

2. File retrieve

3. File delete

Checklist

• I formatted the code cargo +nightly fmt --all
• I addressed lints thrown by cargo clippy
• I reviewed the submitted code
• I added unit tests for my changes where possible
• I added a CHANGELOG entry if applicable