stdout/stderr around
A lot of functions in the cmd and ctl packages were passing these
around and barely using them. Replaced them with a logger for most
functions. Some functions get an io.Writer instead so that their
tests can find the output they're looking for.
More cleanup on fb-1766: reworked the tests that were using io.Pipe
or os.Pipe to check their results so they now use a bytes.Buffer.
Unexported some variables that didn't need to be exported.
Fixed NewConfigCommand to use the provided stderr, not os.Stderr.
Added tests for rbf_dump, rbf_page, and keygen, since those weren't
being tested at all.
Added chksum_test, final cleanup.
* Add CleanOAuthConfig endpoint
We will use this to get the OAuthConfig information, without the client secret, from
FeatureBase without having to have access to the config file. This will be useful
for the auth-token subcommand.
* Add string manipulation utility functions
Go doesn't have native support for these kind of things, so I added this to make it
easier to do string reversal, and replacing the first string encountered from the
end of the string to the front.
* Add auth-token subcommand
This is for work on [FB-1379](https://molecula.atlassian.net/browse/FB-1379).
We need this new auth-token subcommand to allow users to get access and refresh
tokens without having to login to featurebase via the UI. This commit adds that
functionality.
* error on oauth endpoint if auth isn't on
* https as default scheme in cmd, not internalclient
