Exp database populator: migrate auth scheme

[Tom-Willemsen]

Issue Description

BusApps are turning off the old auth api in Feburary 2025 and so it will stop working then.

openapi specs in yaml and json copied to \\isis\shares\ISIS_Experiment_Controls\data for tickets\Ticket8631. We can contact JA from busapps teams if we have questions.

#8628 will be either a prerequisite or something we need to do alongside this issue.

How & Where?

https://github.com/ISISComputingGroup/ExperimentDatabasePopulator/blob/master/exp_db_populator/webservices_reader.py#L24

Reproducible (Yes/No)?

Will be reproducible if we attempt to use it after it's turned off

Additional Information

Some details in https://teams.microsoft.com/l/message/19:4e381ff6b5674230a74878b1355eec22@thread.skype/1737043299447?tenantId=3f66361c-a87e-4158-8f61-99e82db3cac8&groupId=d9946ec3-a454-424f-b673-5ffcb9f9ade0&parentMessageId=1737043299447&teamName=IBEX%20Developers&channelName=email-exp-controls&createdTime=1737043299447

Acceptance Criteria

• Uses new api

How to Review

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• Provide verbose instructions for the reviewer to test that your changes work and fix the issue
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• Provide screenshots of the feature to help the reviewer if relevant

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...

_{To the reviewer: Make sure to update submodules!}

[Tom-Willemsen]

As far as I understand BusApps emails, it's just the auth bit that is impacted, we still use SOAP for the main get experiments call I believe.