feat(react): replace user urn with username

[shubham49]

Showing username instead of user's urn.
Added 1 more field in graphql schema for showing username.

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable)

[gabe-lyons]

we can get username by creating a OwnerUrn using OwnerUrn.createFromString() and then extracting name from there. Lets do that instead of string parsing.

[shirshanka]

@gabe-lyons : will this stuff work after no-code?

[gabe-lyons]

OwnerUrn will still exist after no-code, but you're right that we will eventually deprecate and replace it with just the generic Urn class. To use the Urn class, you would create an instance of a generic urn using Urn.createFromString(rawUrn), then access the part of the key you are interested in using urn.getEntityKey().get(index)

[shirshanka]

Instead of
{ author authorUserName }

Should the graphQL be:
{ author { userName } }

that way, you are always traversing from the authorUrn to the CorpUser model to retrieve the userName field. In the case of CorpUser, this can be just the CorpUser resolver + mapper cracking open the urn to retrieve this.

[gabe-lyons]

You can refer to the OwnerMapper for an example of creating a link to another entity

[gabe-lyons]

can you follow the pattern from OwnerMapper I linked to construct a corp user entity just with the actor? Then, you can rely on graphql resolvers to fetch properties like username

[gabe-lyons]

You also will need to create a wiring for InstitutionalMemoryMetadata.author in GmsGraphqlEngine like so: https://github.com/linkedin/datahub/blob/master/datahub-graphql-core/src/main/java/com/linkedin/datahub/graphql/GmsGraphQLEngine.java#L295

[gabe-lyons]

Looks good to me! thanks @shubham49

[shirshanka]

LGTM