Update web hosting api to handle splited transaction

[Neylix]

Description

This PR updates web_hosting API to handle files with their content in another transaction(s).

Fixes #340

Type of change

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

How Has This Been Tested?

Tested with Archethic Website sent by aeweb cli.
Also add tests in test files

To test, refer to archethic-foundation/aeweb-cli#64

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[ghost]

I think you can simplify using simple case:

case get_req_header(conn, "accept_encoding") do
   [] ->
       # Do something when it's empty
    accept_encoding ->
       # Do something when it's not empty
end

[Neylix]

Yes but there will be code duplication because we have the same action to do when accept_encoding is empty and when it is not empty but don't contain "gzip"

[ghost]

You can use with statement to chain conditions