Allow extensions to announce contentType to AppWrapper, make saving images possible

[pascalwengerter]

Description

Necessary for owncloud/web-extensions#43

[update-docs]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would create a changelog item based on your changes.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[dschmidt]

Why do we need this? Can't the extension just use resource.mimeType directly?

I would like to keep the api surface minimal

[dschmidt]

Ah, it's the other way round - the extension needs to tell the mimetype to oC Web because we are only creating a new file?

[pascalwengerter]

Ah, it's the other way round - the extension needs to tell the mimetype to oC Web because we are only creating a new file?

No, it's updating an existing file

[pascalwengerter]

Why do we need this? Can't the extension just use resource.mimeType directly?

I would like to keep the api surface minimal

Open for suggestions regarding the approach. We could check the resource.mimeType (for jpeg/png), but then it's an implicat thing happening in the AppWrapper rathern than the application announcing what it wants to do (albeit the naming/API isn't ideal yet)