feat(rules): Make segment be one of two types

[yquansah]

Make segment under rules respect one of two types.

This:

rules:
  segment: "foo"

Or:

rules:
  segment:
    keys:
    - foo
    - bar
    operator: AND_SEGMENT_OPERATOR

[codecov]

Codecov Report

Merging #1978 (f168d32) into segment-anding (45149d6) will increase coverage by 0.22%.
Report is 5 commits behind head on segment-anding.
The diff coverage is 76.66%.

@@                Coverage Diff                 @@
##           segment-anding    #1978      +/-   ##
==================================================
+ Coverage           70.94%   71.16%   +0.22%     
==================================================
  Files                  67       68       +1     
  Lines                6718     6742      +24     
==================================================
+ Hits                 4766     4798      +32     
+ Misses               1677     1672       -5     
+ Partials              275      272       -3     

Files Changed	Coverage Δ
internal/storage/fs/snapshot.go	68.08% <27.27%> (-1.07%)	⬇️
internal/ext/common.go	84.61% <84.61%> (ø)
internal/ext/exporter.go	85.47% <85.71%> (+2.91%)	⬆️
internal/ext/importer.go	71.11% <100.00%> (+4.22%)	⬆️

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[markphelps]

lgtm! very nice