CASE 1: no extension
CASE 2: extension in upper case
CASE 3: .png
CASE 4: .jpg, .jpeg
CASE 5: .webp
CASE 6: .gif
CASE 7: .bmp
CASE 8: .tif
CASE 9: .heif
CASE 10: .heic
CASE 11: .ico
CASE 12: .svg
CASE 13: ? - avif
CASE 14: ? - ppm
CASE 15: unsupported format by OpenAI + leading space + query params
CASE 16: long URL (supported extension)
CASE 17: long URL (unsupported extension)
CASE 18: non-existing image (supported extension)
CASE 19: non-existing image (unsupported extension)
CASE 21: single word
CASE 22: link to a site
CASE 23: link to a valid PDF file
CASE 24: link to invalid PDF file