[dev] Add mock accessioning server

[StephenHulme]

A vanilla Python implementation of a the ENA accessioning service for development and testing purposes.

• Can be set to always fail, always succeed, or to succeed or fail with random HTTP status codes
• Specifically developed to work with the ENA Webin REST V1 API, a version 2 is recommended for new projects
• Displays the sent payloads for debugging
• Works out the box with Sequencescape's development config: python mock_accessioning_server.py

Usage example:

$ python mock_accessioning_server.py --always-succeed
Mock accession server running
  (configured to always succeed)
Listening on http://localhost:9999

--- Incoming Request ---
Path: /accession_service/
Headers:
  User-Agent: Sequencescape Accessioning V1 Client
  Content-Type: multipart/form-data; boundary=-----------RubyMultipartPost-a4c26aa3f520b5b8c9b83a1b23a9691c
  Content-Length: 1781
  Authorization: Basic ZXJhX2FjY2Vzc2lvbl9sb2dpbjplcmFfYWNjZXNzaW9uX3Bhc3N3b3Jk
  Accept-Encoding: gzip;q=1.0,deflate;q=0.6,identity;q=0.3
  Accept: */*
  Host: localhost:9999
Body:
-------------RubyMultipartPost-a4c26aa3f520b5b8c9b83a1b23a9691c
Content-Disposition: form-data; name="SUBMISSION"; filename="da4021c2-3a5b-11f1-8097-060cfcc4e09f-2026-08-18T124819Z.submission.xml"
Content-Length: 413
Content-Type: text/plain
Content-Transfer-Encoding: binary

<?xml version="1.0" encoding="UTF-8"?><SUBMISSION xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" center_name="SC" broker_name="" alias="da4021c2-3a5b-11f1-8097-060cfcc4e09f-2026-08-18T12:48:19Z" submission_date="2026-08-18T12:48:19Z"><ACTIONS><ACTION><ADD source="da4021c2-3a5b-11f1-8097-060cfcc4e09f-2026-08-18T124819Z.sample.xml" schema="sample"/></ACTION><ACTION><HOLD/></ACTION></ACTIONS></SUBMISSION>

-------------RubyMultipartPost-a4c26aa3f520b5b8c9b83a1b23a9691c
Content-Disposition: form-data; name="SAMPLE"; filename="da4021c2-3a5b-11f1-8097-060cfcc4e09f-2026-08-18T124819Z.sample.xml"
Content-Length: 739
Content-Type: text/plain
Content-Transfer-Encoding: binary

<?xml version="1.0" encoding="UTF-8"?><SAMPLE_SET xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><SAMPLE alias="da4021c2-3a5b-11f1-8097-060cfcc4e09f"><TITLE>sample_1_SQPD-9873_B1</TITLE><SAMPLE_NAME><TAXON_ID>9606</TAXON_ID><COMMON_NAME>Homo sapiens</COMMON_NAME></SAMPLE_NAME><SAMPLE_ATTRIBUTES><SAMPLE_ATTRIBUTE><TAG>geographic location (country and/or sea)</TAG><VALUE>not provided</VALUE></SAMPLE_ATTRIBUTE><SAMPLE_ATTRIBUTE><TAG>collection date</TAG><VALUE>not provided</VALUE></SAMPLE_ATTRIBUTE><SAMPLE_ATTRIBUTE><TAG>sample description</TAG><VALUE>SD-SQPD-9873</VALUE></SAMPLE_ATTRIBUTE><SAMPLE_ATTRIBUTE><TAG>ArrayExpress-SPECIES</TAG><VALUE>Homo sapiens</VALUE></SAMPLE_ATTRIBUTE></SAMPLE_ATTRIBUTES></SAMPLE></SAMPLE_SET>

-------------RubyMultipartPost-a4c26aa3f520b5b8c9b83a1b23a9691c--

-----------------------

127.0.0.1 - - [18/Aug/2026 13:48:19] "POST /accession_service/ HTTP/1.1" 200 -

Changes proposed in this pull request

• Add a local accessioning server for development use

TODO: decide which directory it should live in - or if the repository root is fine.

Instructions for Reviewers

[All PRs] - Confirm PR template filled
[Feature Branches] - Review code
[Production Merges to main]
    - Check story numbers included
    - Check for debug code
    - Check version

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.67%. Comparing base (ebb6588) to head (8e87dac).
⚠️ Report is 7 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #5995      +/-   ##
===========================================
- Coverage    83.71%   83.67%   -0.04%     
===========================================
  Files         1286     1286              
  Lines        31601    31605       +4     
  Branches      3492     3492              
===========================================
- Hits         26455    26446       -9     
- Misses        4332     4341       +9     
- Partials       814      818       +4     

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javascript	85.29% <ø> (ø)
ruby	83.53% <ø> (-0.04%)	⬇️

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