Change FastMCP logger namespace from "FastMCP" to "fastmcp"

[jlowin]

Enhancement

Currently the logging module uses "FastMCP.{name}" to namespace FastMCP loggers, which is nonstandard. It should match the package name and be lowercase: "fastmcp.{name}".

This might constitute a breaking change so it should either be done in the 2.13 release OR we should create both (which could have adverse affects). (Note: investigate this, it might be considered a bugfix under all circumstances)

Note that the TimingMiddleware currently uses the lowercase namespace.

[jlowin]

@strawgate do you have an opinion on whether this would constitute a breaking change (e.g. do we expect people to have behavior that depends on them knowing the prefixed name of a logger?) I'm doing a deep dive on our logging set up.

[strawgate]

I've been meaning to mention.... 😅 that this is inconsistent and that there are already a couple of places using fastmcp -- I think basically anywhere calling getLogger directly is using lowercase.

Historically, it's actually been quite hard to configure logging, with the server resetting any custom handlers fairly often up until recently

Plus the fast MCP logger does not propagate logs to the root logger, so a user would have to explicitly do something to intercept the fast MCP logs (which up until recently would have been difficult).

So while I do think it's a breaking change, I think that someone is broken no matter what we do and the number of people who break is likely to be low.

We also may be able to log a warning to the old logger on startup, with propagation turned off it won't print anything for normal users but anyone who has added a handler would see the warning

[jlowin]