Metadata: add a function to access the stream map

[Jmgr]

This PR adds a function to access the stream map when fetching metadata. The current API only allows you to get a SteamInfo using a stream name.

[tylertreat]

I think we ought to return a copy of the map rather than the actual underlying one? Just to prevent the ability to manipulate it from outside of Metadata.

[Jmgr]

Hm yes that would be more coherent with the other functions. I'll make that change.

Shouldn't StreamInfo.Partitions() also return a copy in that case?

[Jmgr]

I have made the change in aee6d4c.

I have also committed a code simplification in 8f9c1e0. Performance should be the same, so it's only a cosmetic change. What do you think?

[Jmgr]

Also, shouldn't those changes be made in the v2 module?

[tylertreat]

Apologies for the delay on the response, was out all week.

Yeah, we should include the changes in the v2 module.

[Jmgr]

Yeah, we should include the changes in the v2 module.

I have applied the changes to v2 metadata.go file and removed new function from v1.

[tylertreat]

I have applied the changes to v2 metadata.go file and removed new function from v1.

Since the change is backwards compatible, it's OK to include in v1 if you are reliant upon v1 of the module. I think larger API changes will only be applied to v2 going forward but I think it's fine to backport smaller changes to v1.

[Jmgr]

Since the change is backwards compatible, it's OK to include in v1 if you are reliant upon v1 of the module. I think larger API changes will only be applied to v2 going forward but I think it's fine to backport smaller changes to v1.

Alright. I have reverted the function removal from v1.