#1335 file transfer http api

[cmosd]

Proposed changes

Exposing REST endpoints to exchange binary files between a thin-edge connected device and child devices.

Types of changes

• [x] New feature (non-breaking change which adds functionality)

Paste Link to the issue

• #1335

Checklist

• [x] I have read the CONTRIBUTING doc
• [x] I have signed the CLA (in all commits with git commit -s)
• [x] I ran cargo fmt as mentioned in CODING_GUIDELINES
• [x] I used cargo clippy as mentioned in CODING_GUIDELINES
• [x] I have added tests that prove my fix is effective or that my feature works