In the auctionConfig there is a json attribute called perBuyerSignals that list the buyer's domain and it appears optional values. As perBuyerSignals is generated by the Seller and passed to generateBid function of the Buyer, what can be inserted as values. Can this be arbitrarily defined by the Seller?

[const myAuctionConfig = {
'seller': 'https://www.example-ssp.com',
'decisionLogicURL': ...,
'trustedScoringSignalsURL': ...,
'maxTrustedScoringSignalsURLLength': 10000,
'interestGroupBuyers': ['https://www.example-dsp.com', 'https://buyer2.com', ...],
'auctionSignals': {...},
'requestedSize': {'width': '100sw', 'height': '200px'},
'allSlotsRequestedSizes': [{'width': '100sw', 'height': '200px'}, {'width': '200px', 'height': '300px'}, ...],
'directFromSellerSignalsHeaderAdSlot': 'adSlot/1',
'sellerSignals': {...},
'sellerTimeout': 100,
'sellerExperimentGroupId': 12345,
'perBuyerSignals': {'https://www.example-dsp.com': ...,
'https://www.another-buyer.com': ...,
...},
'perBuyerTimeouts': {'https://www.example-dsp.com': 50,
'https://www.another-buyer.com': 200,
'': 150,
...},
'perBuyerCumulativeTimeouts': {'https://www.example-dsp.com': 500,
'https://www.another-buyer.com': 600,
'': 450,
...},
'perBuyerGroupLimits': {'https://www.example-dsp.com': 2,
'https://www.another-buyer.com': 1000,
'': 15,
...},
'perBuyerPrioritySignals': {'https://www.example-dsp.com': {'signal1': 2.5,
'signal2': 2.5,
...},
'https://www.another-buyer.com': {...},
'': {...},
...},
'perBuyerExperimentGroupIds': {'https://www.example-dsp.com': 234,
'https://www.another-buyer.com': 345,
'': 456,
...},
'perBuyerCurrencies': {'https://example.co.uk': 'GBP',
'https://example.fr': 'EUR',
'': 'USD'},
'perBuyerMultiBidLimits': {'https://example.com': 10, '': 5},
'sellerCurrency:' : 'CAD',
'reportingTimeout' : 200,
'deprecatedRenderURLReplacements':{'${SELLER}':'exampleSSP',
'%%SELLER_ALT%%':'exampleSSP'},
'componentAuctions': [
{'seller': 'https://www.some-other-ssp.com',
'decisionLogicURL': ...,
...},
...
],
'signal': / optionally, an AbortSignal /...,
'resolveToConfig': / optionally, a boolean */...,
};
const result = await navigator.runAdAuction(myAuctionConfig);

// If result is a FencedFrameConfig object, it must be used with a fenced frame
// element via its config attribute. Otherwise, it's a urn:uuid for an iframe.
if (window.FencedFrameConfig && result instanceof FencedFrameConfig)
fencedFrame.config = result;
else
iframe.src = result;](url)