Split off -core module.
Change-Id: I64d3c195db94e92da44c7e4971f5e85991ac30c8
diff --git a/core/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/package-info.java b/core/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/package-info.java
new file mode 100644
index 0000000..2f4c7ce
--- /dev/null
+++ b/core/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/package-info.java
@@ -0,0 +1,191 @@
+/**
+ * Provides structured logging to standard output according to the Google Cloud Logging
+ * specification.
+ *
+ * <ul>
+ * <li><a href="#sect-summary">Summary</a>
+ * <li><a href="#sect-activation">Activation</a>
+ * <li><a href="#sect-usage">Usage</a>
+ * </ul>
+ *
+ * <h2 id="sect-summary">Summary</h2>
+ *
+ * <p>This package contains a log formatter for JBoss Logging in the form of a Quarkus plugin that
+ * implements the <a href="https://cloud.google.com/logging/docs/structured-logging">Google Cloud
+ * Logging JSON format</a> on standard output.
+ *
+ * <p>It is possible to log unstructured text, structured data, or a mixture of both depending on
+ * the situation.
+ *
+ * <h2 id="sect-activation">Installation</h2>
+ *
+ * <ul>
+ * <li><a href="#sect-installation-maven">Installation with Maven</a>
+ * <li><a href="#sect-installation-gradle">Installation with Gradle</a>
+ * </ul>
+ *
+ * <p>Add the runtime POM to your dependency list. As long as the JAR is on the classpath at both
+ * build time and runtime, the log formatter automatically registers itself on startup.
+ *
+ * <h3 id="sect-installation-maven">Installation with Maven</h3>
+ *
+ * <pre>{@code
+ * <project>
+ * ...
+ *
+ * <dependencies>
+ * ...
+ *
+ * <dependency>
+ * <groupId>eu.mulk.quarkus-googlecloud-jsonlogging</groupId>
+ * <artifactId>quarkus-googlecloud-jsonlogging-core</artifactId>
+ * <version>4.0.0</version>
+ * </dependency>
+ *
+ * ...
+ * </dependencies>
+ *
+ * ...
+ * </project>
+ * }</pre>
+ *
+ * <h3 id="sect-installation-gradle">Installation with Gradle</h3>
+ *
+ * <pre>{@code
+ * dependencies {
+ * ...
+ *
+ * implementation("eu.mulk.quarkus-googlecloud-jsonlogging:quarkus-googlecloud-jsonlogging-core:4.0.0")
+ *
+ * ...
+ * }
+ * }</pre>
+ *
+ * <h2 id="sect-usage">Usage</h2>
+ *
+ * <ul>
+ * <li><a href="#sect-usage-parameter">Using Label and StructuredParameter</a>
+ * <li><a href="#sect-usage-provider">Using LabelProvider and StructuredParameterProvider</a>
+ * <li><a href="#sect-usage-mdc">Using the Mapped Diagnostic Context</a>
+ * </ul>
+ *
+ * <p>Logging unstructured data requires no code changes. All logs are automatically converted to
+ * Google-Cloud-Logging-compatible JSON.
+ *
+ * <p>Structured data can be logged in one of 3 different ways: by passing {@link
+ * eu.mulk.quarkus.googlecloud.jsonlogging.Label}s and {@link
+ * eu.mulk.quarkus.googlecloud.jsonlogging.StructuredParameter}s as parameters to individual log
+ * entries, by supplying {@link eu.mulk.quarkus.googlecloud.jsonlogging.LabelProvider}s and {@link
+ * eu.mulk.quarkus.googlecloud.jsonlogging.StructuredParameterProvider}s, or by using the Mapped
+ * Diagnostic Context.
+ *
+ * <h3 id="sect-usage-parameter">Using Label and StructuredParameter</h3>
+ *
+ * <p>Instances of {@link eu.mulk.quarkus.googlecloud.jsonlogging.Label} and {@link
+ * eu.mulk.quarkus.googlecloud.jsonlogging.StructuredParameter} can be passed as log parameters to
+ * the {@code *f} family of logging functions on JBoss Logging's {@link org.jboss.logging.Logger}.
+ *
+ * <p>Simple key–value pairs are represented by {@link
+ * eu.mulk.quarkus.googlecloud.jsonlogging.KeyValueParameter}.
+ *
+ * <p><strong>Example:</strong>
+ *
+ * <pre>{@code
+ * logger.logf(
+ * "Request rejected: unauthorized.",
+ * Label.of("requestId", "123"),
+ * KeyValueParameter.of("resource", "/users/mulk"),
+ * KeyValueParameter.of("method", "PATCH"),
+ * KeyValueParameter.of("reason", "invalid token"));
+ * }</pre>
+ *
+ * Result:
+ *
+ * <pre>{@code
+ * {
+ * "jsonPayload": {
+ * "message": "Request rejected: unauthorized.",
+ * "resource": "/users/mulk",
+ * "method": "PATCH",
+ * "reason": "invalid token"
+ * },
+ * "labels": {
+ * "requestId": "123"
+ * }
+ * }
+ * }</pre>
+ *
+ * <h3 id="sect-usage-provider">Using LabelProvider and StructuredParameterProvider</h3>
+ *
+ * <p>If you pass {@link eu.mulk.quarkus.googlecloud.jsonlogging.LabelProvider}s and {@link
+ * eu.mulk.quarkus.googlecloud.jsonlogging.StructuredParameterProvider}s to {@link
+ * eu.mulk.quarkus.googlecloud.jsonlogging.Formatter}, then they are consulted to provide labels and
+ * parameters for each message that is logged. This can be used to provide contextual information
+ * such as tracing and request IDs stored in thread-local storage.
+ *
+ * <p>If you are using the Quarkus extension, CDI beans that implement these interfaces are
+ * automatically detected at build time and passed to the formatter on startup.
+ *
+ * <p><strong>Example:</strong>
+ *
+ * <pre>{@code
+ * @Singleton
+ * @Unremovable
+ * public final class TraceLogParameterProvider implements StructuredParameterProvider, LabelProvider {
+ *
+ * @Override
+ * public StructuredParameter getParameter() {
+ * var b = Json.createObjectBuilder();
+ * b.add("traceId", Span.current().getSpanContext().getTraceId());
+ * b.add("spanId", Span.current().getSpanContext().getSpanId());
+ * return () -> b;
+ * }
+ *
+ * @Override
+ * public Collection<Label> getLabels() {
+ * return List.of(Label.of("requestId", "123"));
+ * }
+ * }
+ * }</pre>
+ *
+ * Result:
+ *
+ * <pre>{@code
+ * {
+ * "jsonPayload": {
+ * "message": "Request rejected: unauthorized.",
+ * "traceId": "39f9a49a9567a8bd7087b708f8932550",
+ * "spanId": "c7431b14630b633d"
+ * },
+ * "labels": {
+ * "requestId": "123"
+ * }
+ * }
+ * }</pre>
+ *
+ * <h3 id="sect-usage-mdc">Using the Mapped Diagnostic Context</h3>
+ *
+ * <p>Any key–value pairs in JBoss Logging's thread-local {@link org.jboss.logging.MDC} are added to
+ * the resulting JSON.
+ *
+ * <p><strong>Example:</strong>
+ *
+ * <pre>{@code
+ * MDC.put("resource", "/users/mulk");
+ * MDC.put("method", "PATCH");
+ * logger.logf("Request rejected: unauthorized.");
+ * }</pre>
+ *
+ * Result:
+ *
+ * <pre>{@code
+ * {
+ * "jsonPayload": {
+ * "message": "Request rejected: unauthorized.",
+ * "resource": "/users/mulk",
+ * "method": "PATCH"
+ * }
+ * }
+ * }</pre>
+ */
+package eu.mulk.quarkus.googlecloud.jsonlogging;