3 years is a very conservative limit that allows for a very wide buffer
for year-over-year analysis. The max is set to 5 years because that is
the policy listed for logging in hosted Discourse.
https://meta.discourse.org/t/search-logs-page/73281/11?u=techapj
This commit adds following features:
- support for tracking click through to user, tag and category
- new filter for search type (header, full page)
This commit also removes "most viewed topic" field from search logs page because we are now tracking multiple click through entities, so topic is not a special entity anymore. This also improves query perf. The query now takes `20.5ms` to runs, as opposed to `655.9ms` previously.
