Use `direct_asset_path` instead of `filepath` when calling Releases or Release Links APIs

Overview

The Release and Release Links APIs accept a filepath parameter which represents a permanent link to an asset.

This parameter will be deprecated and removed in %17.0, and an alias (e.g. direct_asset_path) will be available to use instead.

That alias will be available starting in %15.9 (check gitlab#273757 (closed) to keep track of progress).

We want to ensure any references to the old parameter in the CLI is replaced with direct_asset_path moving forward.

Proposal

We accept release asset links as json – see here and here, so unless this had changed since this proposal was written, we basically need to ensure users of the CLI is aware of that change by doing the following:

• Update example of the json accepted in command documentation to use direct_asset_path.
• Update example of the json accepted in flag declaration to use direct_asset_path.