0.19.0

• Weaviate integration by @Heezer
• DOC, XLS and PPT loaders by @oognuyh
• Separate chat memory for each user
• Custom in-process embedding models
• Added lots of Javadoc
• Added DocumentTransformer and it's first implementation: HtmlTextExtractor
• OpenAiTokenizer is now more precise and can estimate tokens for tools/functions
• Added option to force tool/function execution in OpenAiChatModel and OpenAiStreamingChatModel
• Some bugfixes and improvements