capture mongodb database name as mongo-db.name attribute instead of client description

[imavroukakis]

Closes #1376

[imavroukakis]

It should probably be discussed what is to be done with the client description and a sensible fallback when a dbName doesn't exist.

Client Description: Should it be added to SemanticAttributes?
Empty/Null database name: Client description might not be a sensible fallback, is returning null acceptable?

[iNikem]

If db.name is not available, then it is totally Ok to return null. What else can we do? I even think we can remove the current fallback to description.

[imavroukakis]

If db.name is not available, then it is totally Ok to return null. What else can we do? I even think we can remove the current fallback to description.

Makes sense. Should client description also be captured if available? That would be outside the scope of this PR, but would be good to get an opinion.

[iNikem]

Should client description also be captured if available?

If some MongoDB user thinks that this information is useful, then yes. After the corresponding PR to the spec :)

[trask]

Thanks @imavroukakis!