Closes #923 - Added initiator beacon requirement to EUM Server

[JonasKunz]

Closes #923

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This change is 

[mariusoe]

Reviewed 4 of 4 files at r1.
Reviewable status: all files reviewed, 7 unresolved discussions (waiting on @JonasKunz)

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components/inspectit-ocelot-eum-server/src/main/java/rocks/inspectit/oce/eum/server/configuration/model/BeaconRequirement.java, line 63 at r1 (raw file):

    private RequirementType requirement;

    private List<InitiatorType> initiators = Arrays.asList(InitiatorType.values());

Please add some docs to this field as well

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components/inspectit-ocelot-eum-server/src/main/java/rocks/inspectit/oce/eum/server/configuration/model/BeaconRequirement.java, line 67 at r1 (raw file):

    /**
     * The field which is targeted.
     * Used for the "EXISTS" and "NOT_EXISTS" requirement types.

Can you use {@link RequirementType#EXISTS} in the docs, then there is a link to the acutal enums

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components/inspectit-ocelot-eum-server/src/main/java/rocks/inspectit/oce/eum/server/configuration/model/InitiatorType.java, line 35 at r1 (raw file):

hasType

How about naming this isEqualTo? Imo hasType feels somehow wrong for this method.
Or just overloading the method by hasInitiator(String)

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components/inspectit-ocelot-eum-server/src/main/java/rocks/inspectit/oce/eum/server/configuration/model/InitiatorType.java, line 37 at r1 (raw file):

    abstract boolean hasType(String httpInitiatorValue);

    public boolean hasInitiator(Beacon beacon) {

please add a small docu

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components/inspectit-ocelot-eum-server/src/test/java/rocks/inspectit/oce/eum/server/configuration/model/BeaconRequirementTest.java, line 144 at r1 (raw file):

nullInitiator

Maybe we should adjust the test namings so we don't have a mix between camel and snake casing

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components/inspectit-ocelot-eum-server/src/test/java/rocks/inspectit/oce/eum/server/configuration/model/BeaconRequirementTest.java, line 153 at r1 (raw file):

            assertThat(result).isFalse();
        }
    }

It would be good to have a test for the document as well because that is a bit special with its null check.

@Test
public void documentInitiator() {
    Beacon beacon = Beacon.of(Collections.emptyMap());
    requirement.setInitiators(Collections.singletonList(InitiatorType.DOCUMENT));
    requirement.setRequirement(BeaconRequirement.RequirementType.HAS_INITIATOR);

    boolean result = requirement.validate(beacon);

    assertThat(result).isTrue();
}

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inspectit-ocelot-documentation/docs/enduser-monitoring/eum-server-configuration.md, line 158 at r1 (raw file):

The following requirement types are currently be supported:

| Type | Note |

How about adding this table to the top, before the example so there is a quick overview on existing requirement types?

[mariusoe]

Reviewable status: all files reviewed, 8 unresolved discussions (waiting on @JonasKunz)

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components/inspectit-ocelot-eum-server/src/main/java/rocks/inspectit/oce/eum/server/configuration/model/BeaconRequirement.java, line 39 at r1 (raw file):

     * The supported types of requirements.
     */
    public enum RequirementType {

Since there is no validation anymore, in my oppinion, we should add a validation due to the fact that some fields are not required in case a specific requirement type is used.
This would also prevent some errors and confused users.
Doing this, the server fails immeditaly when providing a wrong config.

 @AssertTrue
public boolean isValid() {
    switch (requirement) {
        case EXISTS:
        case NOT_EXISTS:
            return field != null && initiators == null;
        case HAS_INITIATOR:
            return field == null && initiators != null;
        default:
            log.error("Requirement of type {} is not supported.", requirement);
            return false;
    }
}

[mariusoe]

Reviewed 4 of 4 files at r2.
Reviewable status: complete! all files reviewed, all discussions resolved