Document Log Injestor API/interface for L2s to submit retrieval logs

[aarshkshah1992]

L2s will periodically submit retrieval logs to the Log injestor service so they can be rewarded in proportion to the retrievals served by them.

To accomplish this, we need to document the Log injestor API/interface that the L2 will have to invoke to submit these logs.

[guanzo]

https://www.notion.so/pl-strflt/Logs-service-d52cb0fd0bff4c3392fc765720d10b81#06739e1c23264aec8f42cda91c1bf4c4