[Features] Add missing trace log.

[developeruche]

#Motivation
While some action is been done on the Indexer server, some logs is needed to inform the operation on actions that has been done on the indexer application.

Some sections where logging is needed are;

1. A log indicating that events from the specified block-number is (been queried, query complete).
2. A log to indicate the indexing process has kicked in.

Fell free to add more logs to sections you think it would be necessary.
trace log to indicate init indexing has started and ended and the subscription is on (creating and Issue)