Iss #98 - Initial commit of Github webhooks code

Additionally contains code to move API client models to a separate package to allow for application specific models to live separately from consumed upstream models.

src/main/java/org/eclipsefoundation/git/eca/api/models/GithubAccessToken.java

+/**
+ * Copyright (c) 2022 Eclipse Foundation
+ *
+ * This program and the accompanying materials are made
+ * available under the terms of the Eclipse Public License 2.0
+ * which is available at https://www.eclipse.org/legal/epl-2.0/
+ *
+ * Author: Martin Lowe <martin.lowe@eclipse-foundation.org>
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.eclipsefoundation.git.eca.api.models;
+
+import java.time.LocalDateTime;
+
+import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
+import com.fasterxml.jackson.databind.annotation.JsonPOJOBuilder;
+import com.google.auto.value.AutoValue;
+
+/**
+ * @author martin
+ *
+ */
+@AutoValue
+@JsonDeserialize(builder = AutoValue_GithubAccessToken.Builder.class)
+public abstract class GithubAccessToken {
+
+    public abstract String getToken();
+    public abstract LocalDateTime getExpiresAt();
+    
+    public static Builder builder() {
+        return new AutoValue_GithubAccessToken.Builder();
+    }
+
+    @AutoValue.Builder
+    @JsonPOJOBuilder(withPrefix = "set")
+    public abstract static class Builder {
+        public abstract Builder setToken(String token);
+        public abstract Builder setExpiresAt(LocalDateTime expiresAt);
+
+        public abstract GithubAccessToken build();
+    }
+}