Expose `TeamsMessage` interface to support mocking #126

Job	Run time
Dependency Updates / Assert PR branch is ahead	3s
Go Module Validation / Assert PR branch is ahead	4s
Lint / Assert PR branch is ahead	2s
Vulnerability / Assert PR branch is ahead	2s
Dependency Updates / Look for available minor or patch releases	24s
Lint / Lint Markdown files	11s
Lint / Lint Dockerfiles	7s
Vulnerability / govulncheck	22s
Go Module Validation / Look for missing go.mod changes	20s
Go Module Validation / Look for missing vendored dependencies	14s
	1m 49s

Provide feedback