Use logging.FromContext instead of logging.Default where possible

[arielshaqed]

Loggers created using logging.FromContext include a request ID field,
allowing readers to thread together actions performed for the same request.
Also in future they allow us to add additional fields, for example to
distinguish S3 from lakeFS API operations deep inside the call tree.

Rename logging.Default to something more descriptive but perhaps less
pleasant, to encourage calling logging.FromContext.

Fixes #2682.

[arielshaqed]

Reviewers, this one is probably easiest to discuss by commit:

• da8b2c0 is all about using logging.FromContext(ctx) instead of logging.Default(). We place fields (request_id) on the context, and this is the only foolproof way to determine the flow of logs for a particular request.
• d8530cd and 666e0c4 try to make it harder to use logging.Default() in future, by changing its name to be less appealing. This is intentional - whenever a context is available, logging.FromContext is the right choice!

[nopcoder]

The adapter use of ctx for logging is great.
But renaming the Default() to ContextUnavailable() looks like we try to force the use of context why we ask for default logger.
Can we rename it back?

[arielshaqed]

The adapter use of ctx for logging is great. But renaming the Default() to ContextUnavailable() looks like we try to force the use of context why we ask for default logger. Can we rename it back?

Yes, indeed! I really want to make it unpleasant to use a logger without providing a context. It is almost always correct to provide a context to get a logger.

Would you be happier if I improved its godoc?

[nopcoder]

The adapter use of ctx for logging is great. But renaming the Default() to ContextUnavailable() looks like we try to force the use of context why we ask for default logger. Can we rename it back?

Yes, indeed! I really want to make it unpleasant to use a logger without providing a context. It is almost always correct to provide a context to get a logger.

Would you be happier if I improved its godoc?

No need to improve the godocs - approved.
Will try to think of a better way of using it.
Usually I'll have a logger in place and just need to pass the context - don't want that to be mix with getting a fresh logger from context.
If I'll have something better I'll suggest in a different PR.

[arielshaqed]

The adapter use of ctx for logging is great. But renaming the Default() to ContextUnavailable() looks like we try to force the use of context why we ask for default logger. Can we rename it back?

Yes, indeed! I really want to make it unpleasant to use a logger without providing a context. It is almost always correct to provide a context to get a logger.
Would you be happier if I improved its godoc?

No need to improve the godocs - approved. Will try to think of a better way of using it. Usually I'll have a logger in place and just need to pass the context - don't want that to be mix with getting a fresh logger from context. If I'll have something better I'll suggest in a different PR.

Thanks... pulling!

I've been thinking about your idea. The point is that we already had Logger.WithContext: it adds the context onto an existing logger. But nobody used it! One way to force it would be to call Logger-without-context "LoggerBuilder" or "LoggerTemplate", and not have any logging methods on it. And you'd need to call "LoggerBuilder.WithTemplate" to get a Logger. Anyway, that's for another day.