HB-2148 PBS Adapter support bidder specific options

[idettman]

Type of change

• [X ] Feature

Description of change

Feature allow pubs to insert an 'adapterOptions' parameter in s2sConfig that adds arguments to the resulting OpenRTB payload that goes to Prebid Server.

pbjs.setConfig({
  s2sConfig: {
    adapterOptions: {
      rubicon: {singleRequest: false}
    }
  }
});

// With this argument, the PBJS PBS adapter would insert the following ext object:
bidRequest: {
    ext: {
        rubicon: {
            singleRequest: false
        }
    }
}

// multiple bidders
pbjs.setConfig({
  s2sConfig: {
    adapterOptions: {
     rubicon: {singleRequest: false},
     appnexus: {key: "value"}
    }
  }
});

// With this argument, the PBJS PBS adapter would insert the following ext object
bidRequest: {
    ext: {
        rubicon: {
            singleRequest: false
        },
        appnexus: {
             key: "value"
        }
    }
}

• A link to a PR on the docs repo at https://github.com/prebid/prebid.github.io/

Other information

HB-2148

[harpere]

LGTM