add tests for text splitting

make overlap a class member for easier testing

check for ollama availability

move api endpoint init to AbstractModel

This should finally solve the chicken-egg issue. This also renames the
ollama url parameter from baseurl to apiurl and sets a sensible default

test: add test for Ollama model provider

test: add test for Generic model provider

Use Ionos for this test

test: add test for VoyageAI model provider

mark test incomplete on insufficient credits

test: add test for Reka model provider

test: add test for Mistral model provider

fix groq test and temperature issue

test: add test for Groq model provider

fixes based on tests, improve tests

test: add ModelGeminiTest for Gemini AI provider

first few tests to ensure model providers work

add default test workflows