Craft a guide to using Memory in CrewAI please

Can you please provide example doco and code for the following area

RAG
RAG CSV RAG Search - CrewAI, PDF RAG Search - CrewAI etc

Provide working examples, how to agents can access it, how you let them see it, is it global? etc.
Then a simple “poem” like example with it working so we can grok it fully.

Knowledge and Memory

Can you please provide a simple example as to what these mean. Do they mean RAG? do they mean Global Flow variables or Crew specific.

How long do they last, how can we see if they work, how do we clear

Examples

Please provide full examples that are working, also put these in your code tests as things like

# Create a text file knowledge source
text_source = CrewDoclingSource(
    file_paths=["document.txt", "another.txt"]

does not work for me as CrewDoclingSource does not support .txt files but the doco says it does as test rig with all core features would help pick up these issues.

For this

Error loading content: File format not allowed: knowledge/members.txt. Supported formats: [<InputFormat.MD: 'md'>, <InputFormat.ASCIIDOC: 'asciidoc'>, <InputFormat.PDF: 'pdf'>, <InputFormat.DOCX: 'docx'>, <InputFormat.HTML: 'html'>, <InputFormat.IMAGE: 'image'>, <InputFormat.XLSX: 'xlsx'>, <InputFormat.PPTX: 'pptx'>]

I recognise a lot of this is new and you are a growing team so grateful for the doco.