feature request: Associate a string with an asset, without restarting elementds

Our use case is that we are creating certificates of ownership/authenticity for media, that can be purchased and resold. The assets are identified by a signed hash of the media. Thus the signficant "identifier" of the certificate is the signed hash, not the guid constructed by Elements in the issuance. This could be achieved as an asset "name", but we cannot restart elementsd each time a certificate is created.

Best result would be for any node to be able to look up transactions and utxo associated with the string. (Relating to use case: Given the media alone, which contains this signed hash identifier and is thus verifiable, we would like people to be able identify transactions involving it on the blockchain (e.g., who is the rightful owner), without relying on our company's database.)

Acceptable result is for any node to look at some transaction involving the asset (perhaps just the first/issuance?) and see the string.

Fallback is to use data output type, with people crawling the blockchain to find owner.

未指定文件、测试或入口点。首先跟踪与资产标识符相关的资产发行和交易/UTXO查找路径，然后将请求的字符串关联与 data-output 回退进行比较。完成的标准是，节点无需重启 elementsd 即可关联该字符串，并使用它查找相关交易或 UTXO。

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