* fix: Support @contentType for multiline values
Fixes the issue where the @contentType annotation broke the parsing of multiline values.
* chore: add dotall flag to fileExtractContentType
Not strictly needed since body:file uses single-line values in practice,
but doesn't hurt and matches what multipartExtractContentType does.
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Co-authored-by: Márk Dániel Seres <markdaniel.seres@tesco.com>