add httpdata struct to get http auth information from tags in event

[w3irdrobot]

Description

Commit ab36259 added the Kind and Tags to be used for NIP98 events. NIP98 tags contain some metadata that would be great to have easy access to in a struct that knows how to parse the tags and get that information, much like is done with NIP94 FileMetadata. This PR adds an HttpData struct that does just this. This makes it easy to get the necessary data from the tags and also get the tags from the data struct.

Changelog notice

Added HttpData struct for interacting with NIP98 HTTP data

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran make precommit before committing

[yukibtc]

Thanks, is this PR ready?

[w3irdrobot]

should be, unless you'd like me to add some tests

[yukibtc]

utACK a973568