doc: matlab example - parameterize wrapper, document Individual license workflow

[llueg]

Summary

Generalize the matlab-springmass example so other users can run it
with their own MATLAB license:

• Dockerfile.matlab-base is now parameterized with MATLAB_RELEASE
  and MATLAB_USERNAME build args (was hardcoded).
• README now covers both network license (primary path) and
  MATLAB Individual license file workflows.
• The Individual license path requires renaming the ubuntu user
  inside the container — recent MATLAB releases pick ubuntu out of
  /etc/passwd for the file-based license check regardless of the
  actual running UID. Renaming it to the username your license
  authorizes lets the check succeed. Rationale documented in the
  Dockerfile comment.
• Fix existing run/serve examples in the README: --runtime-args
  was used where --docker-args/--env apply, and payloads were
  missing the {"inputs": ...} wrapper.

Test plan

Tested end-to-end with an Individual license. Network license path is
documented based on the previous README but not retested here.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.08%. Comparing base (7cdeb0b) to head (e777201).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #589      +/-   ##
==========================================
- Coverage   77.13%   77.08%   -0.05%     
==========================================
  Files          32       32              
  Lines        4495     4495              
  Branches      739      739              
==========================================
- Hits         3467     3465       -2     
- Misses        726      728       +2     
  Partials      302      302              

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[dionhaefner]

Could something like this technically be done from inside tesseract_api.py at startup? That is, (1) inspect the license file to find out which username it belongs to; (2) manipulate the runtime environment so the username matches? Or maybe even change the username in the release file via text substitution?

(This has a few too many manual steps for my taste, but if it's the best we can do it's what it is.)

[llueg]

This actually was possible with some tweaks, see the latest changes. We need the root user to rename the relevant files in /etc/passwd. One thing I noticed: tesseract build failed for me with the standard Matlab image as base, since it doesn't have root user by default, so the apt-get in Dockerfile.base failed. I added the root user there now - Claude said this was fine since we change it back at the end anyway, and might be useful for other non-root base images. Let me know what you think. It's weird though that this didn't occur in your original PR on this, since you were also using the default Matlab base image. I checked and 2025b also doesn't have a default root user..
Edit: The root issue will also be fixed in #598 .

[llueg]

Oh, and you can read the username from the license file, it's in there in hexadecimal (along with the mac address). Changing the mac address at runtime is a little clunky so I would vote to stick with explicit arguments for both, but I can add it if you think it best.

[PasteurBot]

Benchmark Results

Benchmarks use a no-op Tesseract to measure pure framework overhead.

🚀 0 faster, ⚠️ 5 slower, ✅ 31 unchanged

Notable changes

Benchmark	Baseline	Current	Change	Status
cli/apply_1,000	1631.051ms	2060.859ms	+26.4%	⚠️ slower
cli/apply_100,000	1651.444ms	1948.727ms	+18.0%	⚠️ slower
cli/apply_10,000,000	1701.238ms	2041.576ms	+20.0%	⚠️ slower
http/apply_1,000	2.871ms	3.951ms	+37.6%	⚠️ slower
http/apply_100,000	8.103ms	10.467ms	+29.2%	⚠️ slower

Full results

Benchmark	Baseline	Current	Change	Status
api/apply_1,000	0.501ms	0.497ms	-0.8%	✅
api/apply_100,000	0.498ms	0.499ms	+0.3%	✅
api/apply_10,000,000	0.506ms	0.501ms	-1.0%	✅
cli/apply_1,000	1631.051ms	2060.859ms	+26.4%	⚠️ slower
cli/apply_100,000	1651.444ms	1948.727ms	+18.0%	⚠️ slower
cli/apply_10,000,000	1701.238ms	2041.576ms	+20.0%	⚠️ slower
decoding/base64_1,000	0.029ms	0.029ms	-0.9%	✅
decoding/base64_100,000	0.739ms	0.727ms	-1.5%	✅
decoding/base64_10,000,000	75.929ms	73.819ms	-2.8%	✅
decoding/binref_1,000	0.184ms	0.187ms	+1.1%	✅
decoding/binref_100,000	0.234ms	0.235ms	+0.3%	✅
decoding/binref_10,000,000	10.911ms	11.210ms	+2.7%	✅
decoding/json_1,000	0.099ms	0.099ms	-0.1%	✅
decoding/json_100,000	9.508ms	9.529ms	+0.2%	✅
decoding/json_10,000,000	1136.497ms	1135.492ms	-0.1%	✅
encoding/base64_1,000	0.028ms	0.028ms	+1.8%	✅
encoding/base64_100,000	0.143ms	0.144ms	+1.1%	✅
encoding/base64_10,000,000	24.573ms	23.558ms	-4.1%	✅
encoding/binref_1,000	0.277ms	0.274ms	-0.9%	✅
encoding/binref_100,000	0.447ms	0.450ms	+0.8%	✅
encoding/binref_10,000,000	18.151ms	18.156ms	+0.0%	✅
encoding/json_1,000	0.142ms	0.143ms	+1.1%	✅
encoding/json_100,000	15.370ms	15.186ms	-1.2%	✅
encoding/json_10,000,000	1526.460ms	1527.500ms	+0.1%	✅
http/apply_1,000	2.871ms	3.951ms	+37.6%	⚠️ slower
http/apply_100,000	8.103ms	10.467ms	+29.2%	⚠️ slower
http/apply_10,000,000	697.750ms	697.806ms	+0.0%	✅
roundtrip/base64_1,000	0.058ms	0.058ms	+1.1%	✅
roundtrip/base64_100,000	0.768ms	0.766ms	-0.3%	✅
roundtrip/base64_10,000,000	101.736ms	100.210ms	-1.5%	✅
roundtrip/binref_1,000	0.476ms	0.477ms	+0.2%	✅
roundtrip/binref_100,000	0.688ms	0.683ms	-0.7%	✅
roundtrip/binref_10,000,000	30.361ms	29.104ms	-4.1%	✅
roundtrip/json_1,000	0.248ms	0.247ms	-0.5%	✅
roundtrip/json_100,000	22.346ms	21.349ms	-4.5%	✅
roundtrip/json_10,000,000	2673.340ms	2699.292ms	+1.0%	✅

• Runner: Linux 6.17.0-1013-azure x86_64

[dionhaefner]

I don't understand this sentence. Why would it pick out ubuntu? Doesn't it look for <your-username>?

[llueg]

For some reason, if we don't rename the ubuntu entry, I got an error along the lines of "User ubuntu is not authorized to use this license", regardless of which user name/id I pass to the container.

[dionhaefner]

Closing for now, it seems that MathWorks doesn't support using personal licenses from Docker containers, and the solutions here feel too hacky for an official guide.

Happy to revisit once there's official support on the MATLAB side.