Use fixed version of logger pre release, update dependencies, add test for validate expected error

[ani1311]

$ go test -v -run ^TestLoggerNotWorking$ fortio.org/slack-proxy
=== RUN   TestLoggerNotWorking
{"ts":1700106049.775415,"level":"err","r":34,"file":"main_test.go","line":17,"msg":"Testing logging - err","err":"Channel is not set and Neither attachments, blocks, nor text is set"}
--- PASS: TestLoggerNotWorking (0.00s)
PASS
ok  	fortio.org/slack-proxy	0.154s

fixes ^ shows error now, was showing {}

fixed from fortio/log@df6a201

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (5dc7d1c) 46.78% compared to head (a62e69c) 46.78%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #26   +/-   ##
=======================================
  Coverage   46.78%   46.78%           
=======================================
  Files           4        4           
  Lines         404      404           
=======================================
  Hits          189      189           
  Misses        206      206           
  Partials        9        9           

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[ldemailly]

self "approving"

[ldemailly]

@ani1311 I let you look over this and if you're happy with it: merge and tag/release 0.5.0
(it'll also close the other dependabot PRs as I ran go get -u ./.... && go mod tidy)