Safer encoding

[valentiay]

Do not throw exceptions if illegal characters are encoded

Encoders for strings could throw exceptions if they were used to encode characters, that are not allowed in XML. This was confusing and unexpected behavior. Therefore now such characters are filtered out.

implicit val xmlEncoder: XmlEncoder[String] = XmlEncoder.fromElementEncoder[String]("string")
// Zero character is not allowed
xmlEncoder.encode("\u0000")
// Would throw, but now will output <string/>

Return either from encoding methods

⚠️ This breaks backwards compatibility

Encoders can still throw exceptions, for example, if element name is incorrect, like "1stElement". To handle such errors encoder methods now return Either, not pure values. To keep old behavior -Unsafe methods were added.

Do not throw in decoders

Decoder also could throw exceptions in some cases. Only parsing exceptions were handled. Now decoder can never throw exceptions.