Changes to Install a plugin

added the new optional request property oneOf[#/components/schemas/pkg_api_v1.installPluginRequest]/public_key

added the non-success response with the status 403

added the optional property provenance to the response with the 201 status

added the optional property unsigned to the response with the 201 status

added the new optional request property oneOf[#/components/schemas/pkg_api_v1.installPluginRequest]/allow_unsigned

added the optional property plugin/managed to the response with the 201 status

endpoint added