Azure agent templates throw "Agent template name must be unique" error and deletes the template after downloading JCasC configuration

[Minreaux]

Jenkins and plugins versions report

Environment

Jenkins: 2.426.3
OS: Linux - 6.2.0-1019-azure
Java: 11.0.21 - Ubuntu (OpenJDK 64-Bit Server VM)

ansicolor:1.0.4
antisamy-markup-formatter:162.v0e6ec0fcfcf6
apache-httpcomponents-client-4-api:4.5.14-208.v438351942757
azure-artifact-manager:143.v2b4c2c2d63e5
azure-credentials:312.v0f3973cd1e59
azure-keyvault:237.v301692369180
azure-sdk:157.v855da_0b_eb_dc2
azure-vm-agents:901.ved986df424b_3
bootstrap5-api:5.3.2-3
bouncycastle-api:2.30.1.77-225.v26ea_c9455fd9
branch-api:2.1148.vce12cfcdf090
build-user-vars-plugin:1.9
caffeine-api:3.1.8-133.v17b_1ff2e0599
checks-api:2.0.2
cloud-stats:336.v788e4055508b_
cloudbees-folder:6.858.v898218f3609d
command-launcher:107.v773860566e2e
commons-lang3-api:3.13.0-62.v7d18e55f51e2
commons-text-api:1.11.0-95.v22a_d30ee5d36
configuration-as-code:1775.v810dc950b_514
copyartifact:722.v0662a_9b_e22a_c
credentials:1319.v7eb_51b_3a_c97b_
credentials-binding:657.v2b_19db_7d6e6d
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echarts-api:5.4.3-2
favorite:2.208.v91d65b_7792a_c
font-awesome-api:6.5.1-2
git:5.2.1
git-client:4.6.0
github:1.38.0
github-api:1.318-461.v7a_c09c9fa_d63
github-branch-source:1772.va_69eda_d018d4
gson-api:2.10.1-15.v0d99f670e0a_7
instance-identity:185.v303dc7c645f9
ionicons-api:56.v1b_1c8c49374e
jackson2-api:2.16.1-373.ve709c6871598
jakarta-activation-api:2.0.1-3
jakarta-mail-api:2.0.1-3
javax-activation-api:1.2.0-6
javax-mail-api:1.6.2-9
jaxb:2.3.9-1
jdk-tool:73.vddf737284550
jjwt-api:0.11.5-77.v646c772fddb_0
joda-time-api:2.12.7-29.v5a_b_e3a_82269a_
jquery3-api:3.7.1-1
jsch:0.2.16-86.v42e010d9484b_
json-api:20240205-27.va_007549e895c
json-path-api:2.9.0-33.v2527142f2e1d
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lockable-resources:1232.v512d6c434eb_d
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matrix-auth:3.2.1
matrix-project:822.824.v14451b_c0fd42
metrics:4.2.21-449.v6960d7c54c69
mina-sshd-api-common:2.12.0-90.v9f7fb_9fa_3d3b_
mina-sshd-api-core:2.12.0-90.v9f7fb_9fa_3d3b_
nunit:485.ve8a_85357320d
okhttp-api:4.11.0-172.vda_da_1feeb_c6e
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pipeline-model-extensions:2.2175.v76a_fff0a_2618
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ssh-slaves:2.948.vb_8050d697fec
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windows-azure-storage:419.v4046cd70d2e3
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workflow-basic-steps:1042.ve7b_140c4a_e0c
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workflow-durable-task-step:1331.vc8c2fed35334
workflow-job:1385.vb_58b_86ea_fff1
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workflow-step-api:657.v03b_e8115821b_
workflow-support:865.v43e78cc44e0d
ws-cleanup:0.45

What Operating System are you using (both controller, and any agents involved in the problem)?

Ubuntu 22.04 LTS

Reproduction steps

1. Create a new Azure agent template at your Jenkins instance https://<your-jenkins-url>/manage/cloud/<your-azure-cloud>/new
2. Save the template with any settings
3. Modify the template and save it again
4. Notice that the template can be modified and can save without issue
5. Go to your JCasC page https://<your-jenkins-url>/manage/configuration-as-code/
6. Select "Download Configuration"
7. Go back to your Jenkins Azure templates page https://<your-jenkins-url>/manage/cloud/<your-azure-cloud>/templates and select the same template you created earlier
8. Modify the template and save it again
9. Notice that the template throws "agent template must be unique" error
10. Go back to your Jenkins Azure templates page https://<your-jenkins-url>/manage/cloud/<your-azure-cloud>/templates
11. Notice that the template you created and attempted to modify is now gone

Expected Results

After clicking the "Download Configuration" button for JCasC, I can modify existing Azure agent templates and save them without issue.

Actual Results

After clicking the "Download Configuration" button for JCasC, attempting to modify existing Azure agent templates and saving them throws the "agent template must be unique" error and deletes the template.

Anything else?

Here's a screenshot of the error:

Looks like this error was caused by the changes made in this PR: #493. Or at least that's when the "agent template must be unique" error was introduced.

[Minreaux]

@timja tagging if you have any ideas for the cause of this issue.