feat: allow setting default SSH keys for contexts

[phm07]

[codecov[bot]]

Codecov Report

Attention: 53 lines in your changes are missing coverage. Please review.

Comparison is base (d062965) 45.51% compared to head (b5af99b) 45.91%.

Files	Patch %	Lines
internal/cmd/context/ssh_key.go	74.23%	29 Missing and 13 partials :warning:
internal/cmd/server/enable_rescue.go	0.00%	7 Missing :warning:
internal/cmd/server/create.go	33.33%	3 Missing and 1 partial :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #671      +/-   ##
==========================================
+ Coverage   45.51%   45.91%   +0.40%     
==========================================
  Files         179      186       +7     
  Lines        7879     8248     +369     
==========================================
+ Hits         3586     3787     +201     
- Misses       3837     3991     +154     
- Partials      456      470      +14     

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