added new hm9000 respondent to handle hm9000.start
and hm9000.stop messages
Temporarily mask the 'source' of errors.

[Finishes #58189078]
Add a meaningful 'error_code' to all error responses.

[Finishes #58189188]
Set the buildpack url as custom buildpack if the user uses --buildpack
Ignore the generated doc folder
Fail with more information for debugging
Unpending test
Remove ActiveRecord db setup
send buildpack_key or buildpack_git_url in staging message

keep "buildpack" key in staging message for now, we intend to remove
it once the matching dea code is deployed.

use buildpack_key to send admin buildpacks to use to the DEA
(rather than using the CC URL of the admin buildpack)

don't send buildpack_key when specifying a url and vice versa

disallow special characters in admin buildpack names
Added app API spec
Add noop option for HM9000

More logs in HM9000
v2 service brokers now auth with username/password rather than a token.

[#57183050]
Auto-merge remote-tracking branch 'upstream/master'