enhancement: Enable auth on API explorer page

[charithe]

Allow users to try out the Admin API with credentials.

Signed-off-by: Charith Ellawala charith@cerbos.dev

[codecov]

Codecov Report

Merging #1464 (276c110) into main (138a1cd) will decrease coverage by 0.84%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1464      +/-   ##
==========================================
- Coverage   54.11%   53.28%   -0.84%     
==========================================
  Files         117      106      -11     
  Lines       13132    12087    -1045     
==========================================
- Hits         7106     6440     -666     
+ Misses       5427     5077     -350     
+ Partials      599      570      -29     

Impacted Files	Coverage Δ
internal/server/tests.go	95.15% <0.00%> (-1.82%)	⬇️
cmd/cerbos/repl/internal/directive.go
internal/verify/verify.go
internal/engine/internal/utils.go
cmd/cerbos/repl/internal/cel.go
cmd/cerbos/repl/internal/repl.go
internal/outputcolor/level.go
cmd/cerbos/repl/internal/stack.go
internal/verify/test_fixture.go
cmd/cerbosctl/disable/policy.go
... and 5 more