feat: DIDResolution header changes [DEV-4721]

[sownak]

• new GetPriorityContentType to get prioritized acceptHeader (uses "github.com/timewasted/go-accept-headers" package)
• handles DID Doc only, no DIDDoc metadata for application/did+json, application/did, application/did+ld+json
• handles full resolution for / and application/ld+json;profile="https://w3id.org/did-resolution"
• Moved /metadata route to diddoc/routes

[ankurdotb]

PR reviews should be requested when:

1. Tests are not failing (they currently seem to be failing)
2. PR is not set to draft (that automatically means it's still being worked on)...unless the intention is to ask for a WIP review?

[ankurdotb]

Task linked: DEV-4721 Apply Accept header logic for DID Resolution

[sownak]

@ankurdotb This is a draft PR. The Integration tests are in progress mainly.
The rest can be reviewed with Focus on
services/diddoc/echo_handlers.go

[sownak]

@ankurdotb this PR is ready for review, it also contains @DaevMithran's changes.

@DaevMithran I have modified your resource/metadata code and related testcases, when /metadata or correct profile is asked, we do not have to return the dereferencingMetadata.contentType as the resource's contentType.

[sownak]

Definitely this is now a big PR because the default has been updated in the testcases. Also, I will keep on adding more testcases

[DaevMithran]

Definitely this is now a big PR because the default has been updated in the testcases. Also, I will keep on adding more testcases

@sownak can we target this PR to DEV-4722. So that it's easier to review

[ankurdotb]

Task linked: DEV-4722 Apply Accept header logic for DID URL Dereferencing