Show a warning in the IDE using the XSD when using an incorrect forward (for most pipes)

[thomaspj10]

This is a continuation of:
#7274

I've created a very simple proof of concept:

CustomFrankConfig.xsd:

<xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified"
    xmlns:xs="http://www.w3.org/2001/XMLSchema">

    <xs:element name="Forward">
        <xs:complexType>
            <xs:simpleContent>
                <xs:extension base="xs:string">
                    <xs:attribute type="xs:string" name="name" use="required" />
                    <xs:attribute type="xs:string" name="path" use="required" />
                </xs:extension>
            </xs:simpleContent>
        </xs:complexType>
    </xs:element>

    <xs:element name="FixedResultPipe">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="Forward" minOccurs="0" maxOccurs="unbounded">
                    <xs:complexType>
                        <xs:simpleContent>
                            <xs:extension base="xs:string">
                                <xs:attribute name="name" use="required">
                                    <xs:simpleType>
                                        <xs:restriction base="xs:string">
                                            <xs:enumeration value="success" />
                                            <xs:enumeration value="error" />
                                        </xs:restriction>
                                    </xs:simpleType>
                                </xs:attribute>
                                <xs:attribute type="xs:string" name="path" use="required" />
                            </xs:extension>
                        </xs:simpleContent>
                    </xs:complexType>
                </xs:element>
            </xs:sequence>
            <xs:attribute type="xs:string" name="name" use="required" />
        </xs:complexType>
    </xs:element>

    <xs:element name="EchoPipe">
        <xs:complexType>
            <xs:sequence>
                <xs:element name="Forward" minOccurs="0" maxOccurs="unbounded">
                    <xs:complexType>
                        <xs:simpleContent>
                            <xs:extension base="xs:string">
                                <xs:attribute name="name" use="required">
                                    <xs:simpleType>
                                        <xs:restriction base="xs:string">
                                            <xs:enumeration value="success" />
                                            <xs:enumeration value="echo" />
                                            <xs:enumeration value="exit" />
                                        </xs:restriction>
                                    </xs:simpleType>
                                </xs:attribute>
                                <xs:attribute type="xs:string" name="path" use="required" />
                            </xs:extension>
                        </xs:simpleContent>
                    </xs:complexType>
                </xs:element>
            </xs:sequence>
            <xs:attribute type="xs:string" name="name" use="required" />
        </xs:complexType>
    </xs:element>

    <xs:element name="UnrestrictedForwardPipe">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="Forward" minOccurs="0" maxOccurs="unbounded" />
            </xs:sequence>
            <xs:attribute type="xs:string" name="name" use="required" />
        </xs:complexType>
    </xs:element>

    <xs:element name="Configuration">
        <xs:complexType>
            <xs:sequence>
                <xs:element ref="FixedResultPipe" minOccurs="0" maxOccurs="unbounded" />
                <xs:element ref="EchoPipe" minOccurs="0" maxOccurs="unbounded" />
                <xs:element ref="UnrestrictedForwardPipe" minOccurs="0" maxOccurs="unbounded" />
            </xs:sequence>
        </xs:complexType>
    </xs:element>
</xs:schema>

configuration.xml:

<Configuration
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:noNamespaceSchemaLocation="CustomFrankConfig.xsd"
>
    <FixedResultPipe name="returnResult">
        <Forward name="error" path="ServerError"></Forward>
    </FixedResultPipe>
    <EchoPipe name="doEcho">
        <Forward name="echo" path="Exit404"></Forward>
    </EchoPipe>

    <UnrestrictedForwardPipe name="unrestricted!">
        <Forward name="aaaaa" path=""></Forward>
    </UnrestrictedForwardPipe>
</Configuration>