Context:

For the log observations, we pull and calculate metrics on the first and last months of logs. We don’t expect the first month’s logs to change (after the month has elapsed), and some instances have enough logs (in excess of 100,000) that pulling them is a lot of work.

Goal:

Split the Log Observations into First Month and Last Month, separating output and data fetching. Re-use code where possible.

Acceptance Criteria:

• It is possible to tell the server to pull an observation of just the first month's logs and/or just the last month's logs for a wikibase
• Each observation, whether first month or last month, has the observation date clearly marked in the output

Technical Notes:

Start by folding WikibaseLogObservationModel's fields into WikibaseLogMonthObservationModel.