Add DSA meta field for bidders

[muuki88]

The DSA OpenRTB extension has been merged and prebid along with bidders start implementing support for it.

Like consent support (tcfeu_supported, gpp_sids,...) bidders should be able to indicate if DSA support is available. There are two options to do this.

1. dsa_supported: true / false. Very basic, just saying that a bidder pipes through the dsa objects. Any additional information has to be requested
2. dsa_support: none / list of adrender:1, adrender:2, pubrender:0, pubrender:1, pubrender:2 . Giving additional context what rendering support can be offered. The field and values is just a sketch of the idea.

Both cases can't be vetted by the documentation team, but if bidders claim it, then publisher / ad tech partners can call them out on their docs.

Related issues and PRs

• DSA Control module: toss requests without dsa information Prebid.js#10957
• Consent Management module: enrich requests on regs.ext.dsa Prebid.js#10688
• Prebid Server support for DSA fields prebid-server#3367
• DSA initialization prebid-server#3424

Bidder support

• appnexus Bid Adapter : add DSA support Prebid.js#10971
• Yieldlab Bid Adapter: Add Digital Services Act (DSA) handling Prebid.js#10981
• Rubicon Bid Adapter: pass DSA fields Prebid.js#10974