Support multiple occurrences for custom metadata patterns

[saeub]

Description of the problem

#767 introduced user-specified patterns for extracting metadata that does not belong in the gaze dataframe (like stimulus randomization). For patterns that appear multiple times, the implementation currently only stores the first occurrence in the metadata dictionary. It would be nice if all occurrences could be stored (with timestamps).

See this test (the METADATA_1 pattern occurs twice, but only the first occurrence is stored):

pymovements/tests/unit/utils/parsing_test.py

Line 133 in 0a71116

r'METADATA_1 (?P<metadata_1>\d+)',

Description of a solution

TODO

Minimum acceptance criteria

Reoccurring messages can be extracted using the metadata_patterns argument.

Sample Code

TODO

[dkrako]

ah great, this is related to #887 but here it's related to user-defined patterns instead of the default ones, right? could be a nice follow-up