Changes to Push a plugin

added the new optional header request parameter X-Toolhive-Key-Signing-Capability

added the new optional request property oneOf[#/components/schemas/pkg_api_v1.pushPluginRequest]/key

added the non-success response with the status 403

the request property oneOf[#/components/schemas/pkg_api_v1.pushPluginRequest]/reference became required

added the new optional request property oneOf[#/components/schemas/pkg_api_v1.pushPluginRequest]/identity_token

added the new optional request property oneOf[#/components/schemas/pkg_api_v1.pushPluginRequest]/no_sign

endpoint added