Provide a way to reset SDK safely

[almozavr]

Motivation

Traces could possess user-related sensitive information and e.g.: once user logs out without an internet connection, we don't want unsent traces still be in memory.

Current Situation

There is resetForTest but as the name suggests it seems not 100-production ready. Also, sometimes we see crashes, probably are related to "resetting", happens when initializing the SDK right after calling resetForTest:

Fatal Exception: java.lang.IllegalStateException: GlobalOpenTelemetry.set has already been called. GlobalOpenTelemetry.set must be called only once before any calls to GlobalOpenTelemetry.get. If you are using the OpenTelemetrySdk, use OpenTelemetrySdkBuilder.buildAndRegisterGlobal instead. Previous invocation set to cause of this exception.
       at io.opentelemetry.api.GlobalOpenTelemetry.set(GlobalOpenTelemetry.java:107)
       at co.elastic.apm.android.sdk.ElasticApmAgent.initializeOpentelemetry(ElasticApmAgent.java:305)
       at co.elastic.apm.android.sdk.ElasticApmAgent.onInitializationFinished(ElasticApmAgent.java:228)
       at co.elastic.apm.android.sdk.ElasticApmAgent.initialize(ElasticApmAgent.java:180)
       at co.elastic.apm.android.sdk.ElasticApmAgent.initialize(ElasticApmAgent.java:166)

Proposal

Introduce reliable "reset" or clear all cached traces functionality.

[LikeTheSalad]

Thank you for your feedback.

To make sure I understood correctly, your use case is about stopping the agent from sending data related to a previously authenticated user. If that's the case, do you still need the agent to send telemetry data when there's no user authenticated? I'm asking because I'm wondering if there's a use case where stopping the agent for good might be useful, or if maybe just clearing cache could work in this kind of scenario.