persist topic metadata on disk

[NishanthSpShetty]

lignum currently doesn't store any metadata about the topic, it infers from the topic persisted in disk. Adding this will be good but not necessary as of now

[Ilhan-Personal]

Hey @NishanthSpShetty can i please be assigned this issue? I don't see any contribution docs though can you please point me in the right direction?

[NishanthSpShetty]

@SYSHIL sure, I'm away from my workstation, haven't had the time to setup any documents around it. Feel free to start.

When lignum starts, it reads WAL file to update the in memory buffer message_store.go. I'm thinking about adding a metadata file which stores the details on the topic, from this information we will try to restore the state of the in memory buffer.