[RalphBln]

This PR solves an issue with conflicting timeout settings on different layers of the application.

Spring Boot's internal Tomcat server, which handles all client requests to the API gateway, has its default request timeout set to 30 seconds, while the default API Gateway timeout for requests to connected providers is set to 60 seconds.

In case a federated query took longer than Tomcat's timeout, Tomcat would close the connection to the client prematurely, while the federated request would still be processed in the API gateway. The requested API gateway endpoint would then try to write its response to the client via the meanwhile closed socket, which resulted in an AsyncRequestNotUsableException.

This PR solves the issues by introducing the following changes:

1. We now explicitly set Tomcat's request timeout and make sure it is slightly longer than the API gateway's default timeout (API gateway timeout + 10 seconds).
2. In order to avoid situations where API gateway users select a timeout that is longer than Tomcat's request timeout via the timeout request parameter, we now restrict the maximum value of the timeout request parameters to the API gateway's default timeout, making the API gateway default timeout the maximum timeout.
3. We make the API gateway's default (=maximum) timeout value configurable in the application.properties file via the application.timeout_ms.maxvalue property. The value can also be set from outside via the environment variable REQUEST_TIMEOUT_MS_MAXVALUE. If the variable does not exist the application falls back to a predefined value of 60 seconds (60,000 milliseconds).

Internally, this brought about some internal API changes, especially in the ApiAccessor and the services that instantiate it. Some tests needed to be adapted to the changes.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 52.77778% with 17 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...cs/apigateway/service/AbstractEndpointService.java	46.15%	6 Missing and 1 partial ⚠️
...teway/artefacts/tree/ArtefactsDataTreeService.java	0.00%	5 Missing ⚠️
...tics/apigateway/controller/ols/Ols3Controller.java	0.00%	3 Missing ⚠️
...ics/apigateway/artefacts/search/SearchService.java	50.00%	2 Missing ⚠️

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[RalphBln]

Note: This popped up because the LovPortal seems to have issues at the moment. Requests to it never return leading to the situation with Tomcat closing the client connection prematurely after 30 seconds before the API gateway gives up after its own 60 second timeout.