feat(dashboard): allow admins to impersonate users for debugging

[aicam]

What changes were proposed in this PR?

• Add an admin-only POST /admin/user/impersonate/{uid} endpoint on AdminUserResource that mints a JWT for the target user via the same jwtToken(jwtClaims(user, ...)) path as login; returns 404 for a missing user and 400 for an INACTIVE user.
• Block admin-to-admin impersonation: the endpoint returns 403 when the target has the ADMIN role, and the "Login As" button is disabled for admin rows in the UI.
• Add a per-row "Login As" button in the admin user table (/dashboard/admin/user) that swaps the admin's token for the target user's token, stashing the admin's own token under a separate localStorage key.
• Add a "Stop impersonating" item in the account menu that restores the stashed admin session.

Any related issues, documentation, discussions?

Closes: #6060

How was this PR tested?

• Backend: run sbt "project WorkflowExecutionService" "testOnly org.apache.texera.web.resource.AdminUserResourceSpec", expect 4 passing tests (issued token claims match the target user, 404 for a missing uid, 400 for an INACTIVE user, 403 for an ADMIN target).
• Frontend: run npx ng test --watch=false --include=src/app/common/service/user/user.service.spec.ts from frontend/, expect the impersonation specs to pass (start stashes the admin token and swaps in the target token, stop restores it, isImpersonating reflects state).
• Manual: as an admin, open /dashboard/admin/user, click the Login As button on a REGULAR-user row, confirm the dashboard reloads as that user, then choose "Stop impersonating" from the account menu and confirm the admin session returns.
• Manual (admin guard): confirm the Login As button is disabled on admin rows, and that POST /admin/user/impersonate/{uid} returns 403 for an ADMIN target while a REGULAR target returns 200.

Was this PR authored or co-authored using generative AI tooling?

Co-authored with Claude Opus 4.8 in compliance with ASF

[github-actions]

Automated Reviewer Suggestions

Based on the git blame history of the changed files, we recommend the following reviewers:

• Contributors with relevant context: @jaeyun0503, @Yicong-Huang, @aglinxinyuan
  You can notify them by mentioning @jaeyun0503, @Yicong-Huang, @aglinxinyuan in a comment.

[github-actions]

✅ No material benchmark regressions detected

🟢 2 better · 🔴 0 worse · ⚪ 13 noise (<±5%) · 0 without baseline

Compared against main 24b587f benchmarked on this same runner, so the delta is largely free of cross-runner hardware noise. The "7d avg" column still reflects the gh-pages dashboard. Treat <±5% as noise unless repeated.

Dashboard · Run

	config	throughput	MB/s	latency	max Δ latest / 7d
🟢	bs=10 sw=10 sl=64	418	0.255	23,632/29,784/29,784 us	🟢 -6.5% / 🔴 +94.8%
⚪	bs=100 sw=10 sl=64	820	0.5	121,343/137,213/137,213 us	⚪ within ±5% / 🔴 +26.6%
⚪	bs=1000 sw=10 sl=64	918	0.56	1,094,604/1,125,877/1,125,877 us	⚪ within ±5% / 🔴 +9.7%

Baseline details

Latest main 24b587f from same runner

config	metric	PR	latest main	7d avg	Δ latest	Δ 7d
bs=10 sw=10 sl=64	throughput	418 tuples/sec	428 tuples/sec	770.95 tuples/sec	-2.3%	-45.8%
bs=10 sw=10 sl=64	MB/s	0.255 MB/s	0.261 MB/s	0.471 MB/s	-2.3%	-45.8%
bs=10 sw=10 sl=64	p50	23,632 us	23,060 us	12,775 us	+2.5%	+85.0%
bs=10 sw=10 sl=64	p95	29,784 us	31,854 us	15,286 us	-6.5%	+94.8%
bs=10 sw=10 sl=64	p99	29,784 us	31,854 us	18,795 us	-6.5%	+58.5%
bs=100 sw=10 sl=64	throughput	820 tuples/sec	836 tuples/sec	976.93 tuples/sec	-1.9%	-16.1%
bs=100 sw=10 sl=64	MB/s	0.5 MB/s	0.51 MB/s	0.596 MB/s	-2.0%	-16.1%
bs=100 sw=10 sl=64	p50	121,343 us	118,863 us	102,557 us	+2.1%	+18.3%
bs=100 sw=10 sl=64	p95	137,213 us	135,361 us	108,383 us	+1.4%	+26.6%
bs=100 sw=10 sl=64	p99	137,213 us	135,361 us	115,249 us	+1.4%	+19.1%
bs=1000 sw=10 sl=64	throughput	918 tuples/sec	923 tuples/sec	1,009 tuples/sec	-0.5%	-9.0%
bs=1000 sw=10 sl=64	MB/s	0.56 MB/s	0.563 MB/s	0.616 MB/s	-0.5%	-9.1%
bs=1000 sw=10 sl=64	p50	1,094,604 us	1,082,065 us	997,695 us	+1.2%	+9.7%
bs=1000 sw=10 sl=64	p95	1,125,877 us	1,125,432 us	1,036,731 us	+0.0%	+8.6%
bs=1000 sw=10 sl=64	p99	1,125,877 us	1,125,432 us	1,069,334 us	+0.0%	+5.3%

Raw CSV

config_idx,batch_size,schema_width,string_len,num_batches,total_ms,total_tuples,total_bytes,tuples_per_sec,mb_per_sec,lat_p50_us,lat_p95_us,lat_p99_us
0,10,10,64,20,478.84,200,128000,418,0.255,23631.91,29783.80,29783.80
1,100,10,64,20,2440.44,2000,1280000,820,0.500,121343.09,137212.51,137212.51
2,1000,10,64,20,21784.90,20000,12800000,918,0.560,1094603.78,1125877.02,1125877.02

[codecov-commenter]

Codecov Report

❌ Patch coverage is 83.33333% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 56.91%. Comparing base (a1a7eb0) to head (8f69237).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
...ource/dashboard/admin/user/AdminUserResource.scala	83.33%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6061      +/-   ##
============================================
+ Coverage     56.38%   56.91%   +0.52%     
- Complexity     2986     3064      +78     
============================================
  Files          1129     1129              
  Lines         43794    43814      +20     
  Branches       4743     4746       +3     
============================================
+ Hits          24693    24936     +243     
+ Misses        17650    17445     -205     
+ Partials       1451     1433      -18     

Flag	Coverage Δ		*Carryforward flag
access-control-service	70.00% <ø> (ø)		Carriedforward from 8da519c
agent-service	44.59% <ø> (ø)		Carriedforward from 8da519c
amber	58.69% <83.33%> (+1.38%)	⬆️
computing-unit-managing-service	0.00% <ø> (ø)		Carriedforward from 8da519c
config-service	52.30% <ø> (ø)		Carriedforward from 8da519c
file-service	62.81% <ø> (ø)		Carriedforward from 8da519c
frontend	50.12% <ø> (ø)		Carriedforward from 8da519c
notebook-migration-service	78.57% <ø> (ø)		Carriedforward from 8da519c
pyamber	90.20% <ø> (ø)		Carriedforward from 8da519c
python	90.76% <ø> (ø)		Carriedforward from 8da519c
workflow-compiling-service	55.14% <ø> (ø)		Carriedforward from 8da519c

*This pull request uses carry forward flags. Click here to find out more.

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