Add all parameters to get project of group api (#269)

* Add all parameters listed by
https://docs.gitlab.com/ee/api/groups.html#list-a-groups-projects

src/main/java/org/gitlab4j/api/GroupApi.java

@@ -13,6 +13,7 @@ import org.gitlab4j.api.models.AccessLevel;
 import org.gitlab4j.api.models.Group;
 import org.gitlab4j.api.models.Member;
 import org.gitlab4j.api.models.Project;
+import org.gitlab4j.api.models.ProjectOfGroupFilter;
 import org.gitlab4j.api.models.Visibility;
 
 /**
@@ -224,6 +225,21 @@ public class GroupApi extends AbstractApi {
         return (new Pager<Group>(this, Group.class, itemsPerPage, formData.asMap(), "groups", groupId, "subgroups"));
     }
 
+    /**
+     * Get a list of projects belonging to the specified group ID.
+     *
+     * GET /groups/:id/projects
+     *
+     * @param groupIdOrPath the group ID, path of the group, or a Group instance holding the group ID or path
+     * @param filter the ProjectOfGroupFilter instance holding the filter values for the query
+     * @throws GitLabApiException if any exception occurs
+     */
+  public List<Project> getProjects(Object groupIdOrPath, ProjectOfGroupFilter filter) throws GitLabApiException {
+    GitLabApiForm formData = filter.getQueryParams();
+    Response response = get(Response.Status.OK, formData.asMap(), "groups",  getGroupIdOrPath(groupIdOrPath), "projects");
+    return (response.readEntity(new GenericType<List<Project>>() {}));
+  }
+
     /**
      * Get a list of projects belonging to the specified group ID.
      *

src/main/java/org/gitlab4j/api/models/ProjectOfGroupFilter.java

+package org.gitlab4j.api.models;
+
+import org.gitlab4j.api.Constants.ProjectOrderBy;
+import org.gitlab4j.api.Constants.SortOrder;
+import org.gitlab4j.api.Constants;
+import org.gitlab4j.api.GitLabApiForm;
+
+/**
+ *  This class is used to filter Projects when getting lists of projects for a specified group.
+ */
+public class ProjectOfGroupFilter {
+
+    private Boolean archived;
+    private Visibility visibility;
+    private ProjectOrderBy orderBy;
+    private SortOrder sort;
+    private String search;
+    private Boolean simple;
+    private Boolean owned;
+    private Boolean starred;
+    private Boolean withCustomAttributes;
+    private Boolean withIssuesEnabled;
+    private Boolean withMergeRequestsEnabled;
+
+    /**
+     * Limit by archived status.
+     *
+     * @param archived if true will only return archived projects
+     * @return the reference to this ProjectFilter instance
+     */
+    public ProjectOfGroupFilter withArchived(Boolean archived) {
+        this.archived = archived;
+        return (this);  
+    }
+
+    /**
+     * Limit by visibility public, internal, or private.
+     *
+     * @param visibility the visibility to match
+     * @return the reference to this ProjectFilter instance
+     */
+    public ProjectOfGroupFilter withVisibility(Visibility visibility) {
+        this.visibility = visibility;
+        return (this);       
+    }
+
+    /**
+     * Return projects ordered by id, name, path, created_at, updated_at, or last_activity_at fields. Default is created_at.
+     *
+     * @param orderBy specifies what field to order by
+     * @return the reference to this ProjectFilter instance
+     */
+    public ProjectOfGroupFilter withOrderBy(ProjectOrderBy orderBy) {
+        this.orderBy = orderBy;
+        return (this);
+    }
+
+    /**
+     * Return projects sorted in asc or desc order. Default is desc.
+     *
+     * @param sort sort direction, ASC or DESC
+     * @return the reference to this ProjectFilter instance
+     */
+    public ProjectOfGroupFilter withSortOder(SortOrder sort) {
+        this.sort = sort;
+        return (this);
+    }
+
+    /**
+     * Return list of projects matching the search criteria.
+     *
+     * @param search the search criteria
+     * @return the reference to this ProjectFilter instance
+     */
+    public ProjectOfGroupFilter withSearch(String search) {
+        this.search = search;
+        return (this);
+    }
+
+    /**
+     * Return only limited fields for each project. This is a no-op without 
+     * authentication as then only simple fields are returned.
+     *
+     * @param simple if true, return only limited fields for each project
+     * @return the reference to this ProjectFilter instance
+     */
+    public ProjectOfGroupFilter withSimple(Boolean simple) {
+        this.simple = simple;
+        return (this);
+    }
+
+    /**
+     * Limit by projects explicitly owned by the current user
+     *
+     * @param owned if true, limit to projects explicitly owned by the current user
+     * @return the reference to this ProjectFilter instance
+     */
+    public ProjectOfGroupFilter withOwned(Boolean owned) {
+        this.owned = owned;
+        return (this);
+    }
+
+    /**
+     * Limit by projects starred by the current user.
+     *
+     * @param starred if true, limit by projects starred by the current user
+     * @return the reference to this ProjectFilter instance
+     */
+    public ProjectOfGroupFilter withStarred(Boolean starred) {
+        this.starred = starred;
+        return (this);
+    }
+
+    /**
+     *  Include custom attributes in response (admins only).
+     * 
+     * @param withCustomAttributes if true, include custom attributes in the repsonse
+     * @return the reference to this ProjectFilter instance
+     */
+    public ProjectOfGroupFilter withCustomAttributes(Boolean withCustomAttributes) {
+        this.withCustomAttributes = withCustomAttributes;
+        return (this);
+    }
+
+    /**
+     * Limit by enabled issues feature
+     *
+     * @param withIssuesEnabled if true, limit by enabled issues feature
+     * @return the reference to this ProjectFilter instance
+     */
+    public ProjectOfGroupFilter withIssuesEnabled(Boolean withIssuesEnabled) {
+        this.withIssuesEnabled = withIssuesEnabled;
+        return (this);
+    }
+
+    /**
+     * Limit by enabled merge requests feature
+     *
+     * @param withMergeRequestsEnabled if true, imit by enabled merge requests feature
+     * @return the reference to this ProjectFilter instance
+     */
+    public ProjectOfGroupFilter withMergeRequestsEnabled(Boolean withMergeRequestsEnabled) {
+        this.withMergeRequestsEnabled = withMergeRequestsEnabled;
+        return (this);
+    }
+
+    /**
+     * Get the query params specified by this filter.
+     *
+     * @return a GitLabApiForm instance holding the query parameters for this ProjectFilter instance
+     */
+    public GitLabApiForm getQueryParams() {
+        return (new GitLabApiForm()
+            .withParam("archived", archived)
+            .withParam("visibility", visibility)
+            .withParam("order_by", orderBy)
+            .withParam("sort", sort)
+            .withParam("search", search)
+            .withParam("simple", simple)
+            .withParam("owned", owned)
+            .withParam("starred", starred)
+            .withParam("with_custom_attributes", withCustomAttributes)
+            .withParam("with_issues_enabled", withIssuesEnabled)
+            .withParam("with_merge_requests_enabled ", withMergeRequestsEnabled)
+        );
+    }
+}