Add filesystem client and refactor tests

General MR

Summary

Refactor configuration tests to use a fileystem client that allows us to inject a custom, non-destructive client in. This no longer creates or deletes files on the host system when running the tests.

Relevant logs/screenshots

danieldides@BPH-MAC14 ~/P/b/p/bbctl (dd/add-fs-client)> cat ~/.config/bbctl/config.yaml
bbctl-version: "0.7.5"
bbctl-log-format: "text"
bbctl-log-level: "debug"
bbctl-log-output: "stdout"
big-bang-repo: "/Users/danieldides/Projects/big-bang/bigbang"
big-bang-credential-helper: "credentials-file"
big-bang-credential-helper-credentials-file-path: "/Users/danieldides/.config/bbctl/credentials.yaml"
output-config:
  format: "yaml"
danieldides@BPH-MAC14 ~/P/b/p/bbctl (dd/add-fs-client)> ls -alh ~/.bbctl
ls: /Users/danieldides/.bbctl: No such file or directory
danieldides@BPH-MAC14 ~/P/b/p/bbctl (dd/add-fs-client)> make test
...
danieldides@BPH-MAC14 ~/P/b/p/bbctl (dd/add-fs-client) [1]> cat ~/.config/bbctl/config.yaml
bbctl-version: "0.7.5"
bbctl-log-format: "text"
bbctl-log-level: "debug"
bbctl-log-output: "stdout"
big-bang-repo: "/Users/danieldides/Projects/big-bang/bigbang"
big-bang-credential-helper: "credentials-file"
big-bang-credential-helper-credentials-file-path: "/Users/danieldides/.config/bbctl/credentials.yaml"
output-config:
  format: "yaml"
danieldides@BPH-MAC14 ~/P/b/p/bbctl (dd/add-fs-client)> ls -alh ~/.bbctl
ls: /Users/danieldides/.bbctl: No such file or directory

Linked Issue

Closes #297 (closed)

Upgrade Notices

N/A