Add XML declaration to FM import files (staging/return)

[pdaengeli]

In the course of the pipeline run, import files are created for each category (library/pwl-library.xpl#L90-L113, library/return/1-addPWLid.xsl).

Currently, these files are serialised to disk without any XML declaration. I think it would be sensible to add <?xml version="1.0" encoding="UTF-8" ?> (not sure FileMaker requires this, but it is good to make UTF-8 explicit).

It should be enough to change library/pwl-library.xpl#L109-L111:

            <p:store>
                <p:with-option name="href" select="p:base-uri()"/>
+               <p:with-option name="omit-xml-declaration" select="'false'"/>
            </p:store>

If this doesn't have the desired effect, adding serialisation attributes to xsl:result-document in library/return/1-addPWLid.xsl#L26 might help:

-            <xsl:result-document href="{concat(base-uri() => substring-before('input'),'return/',tokenize(base-uri(),'/')[last()])}">
+            <xsl:result-document method="xml" encoding="UTF-8" href="{concat(base-uri() => substring-before('input'),'return/',tokenize(base-uri(),'/')[last()])}">