fix: add whitelist decorator for file content method

[Alchez]

Closes #81.

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
__init__.py	11	5	54%	10–11, 17–19
customize.py	25	25	0%	1–2, 4, 7–9, 12–19, 24–32, 44–45
hooks.py	15	0	100%
cloud_storage
__init__.py	0	0	100%
cloud_storage/doctype
__init__.py	0	0	100%
cloud_storage/doctype/file_association
__init__.py	0	0	100%
file_association.py	3	0	100%
cloud_storage/doctype/file_version
__init__.py	0	0	100%
file_version.py	3	3	0%	5, 8–9
cloud_storage/overrides
file.py	338	150	55%	48, 55, 83, 88, 95, 104, 110, 142, 145, 155–162, 164–172, 177, 182–183, 187–188, 190–195, 197–200, 202–203, 205, 207, 216, 219–220, 222, 225, 228, 233–234, 237, 240, 251–255, 260, 269, 271–272, 274, 279–283, 286–288, 322, 328, 334, 340, 346, 352, 362, 364–366, 370, 378–380, 382, 396–397, 399, 422–426, 434–435, 438–439, 460–461, 468–469, 484–485, 488, 491–500, 507–508, 510–512, 515–516, 521–523, 525, 530–533, 538, 540, 552–553, 555, 560–564, 566, 571–577
config
__init__.py	0	0	100%
desktop.py	3	3	0%	1, 4–5
docs.py	6	6	0%	1, 3–5, 9–10
tests
conftest.py	26	1	96%	36
test_file.py	90	0	100%
TOTAL	520	193	62%