client: Accept application/json as Text

[diwangs]

ContentType currently does not accept application/json MIME type, which breaks apps like aws-vault.

This PR adds application/json as an acceptable Text secret (since JSON is always a valid UTF-8) and keeps the Text/Blob distinction and MIME parameter parsing intact.

Tested with aws-vault in my NixOS setup:

• Adding secret with it no longer throws aws-vault: error: add: Invalid content type: application/json
• Exporting secret and requesting STS token through it works normally

A more generic fix for this type of errors might be to map every unrecognized content type to Blob instead of rejecting them.

Let me know what you think!

[bilelmoussaoui]

Right, defaulting to blob seems sane but i kind of intentionally made it crash on early versions of the daemon to collect what mimetypes are out there in the wild so i can design the API better in the future.

[diwangs]

Understandable. In that case, consider application/json as another data point. Do you have any comment about the PR itself?

[bilelmoussaoui]

Understandable. In that case, consider application/json as another data point. Do you have any comment about the PR itself?

that would require pulling serde_json, so for now let us keep it as is and we will see later.