ci:config:set truncates strings with `=\n` in them

[reacuna]

What is the current behavior?

When adding a CI config var (i.e. a pipeline config var), that has the string =\n (for example, near the end of RSA private key), heroku cli truncates the value.

heroku ci:config:set TEST_KEY="value\nvalue\nvalue=\nafterequal" -p the-pipeline-name
Setting TEST_KEY... done
TEST_KEY: value\nvalue\nvalue

What is the expected behavior?

heroku cli should set the complete value, as it does when setting an application's config var:

heroku config:set TEST_KEY="value\nvalue\nvalue=\nafterequal" -a the-application-name
Setting TEST_KEY and restarting ⬢ the-application-name... done, v17
TEST_KEY: value\nvalue\nvalue=\nafterequal

heroku cli version: heroku/7.7.1 darwin-x64 node-v10.8.0