Add eitem_type field to EItem and 'MULTIMEDIA' to DOCUMENT_TYPES #1008

Job	Run time
Tests (acquisition, 3.9, pypi, postgresql13, opensearch2)	2m 26s
Tests (acquisition, 3.9, pypi, postgresql14, opensearch2)	2m 27s
Tests (circulation, 3.9, pypi, postgresql13, opensearch2)	7m 46s
Tests (circulation, 3.9, pypi, postgresql14, opensearch2)	7m 29s
Tests (document_requests, 3.9, pypi, postgresql13, opensearch2)	3m 7s
Tests (document_requests, 3.9, pypi, postgresql14, opensearch2)	3m 1s
Tests (ill, 3.9, pypi, postgresql13, opensearch2)	4m 6s
Tests (ill, 3.9, pypi, postgresql14, opensearch2)	3m 34s
Tests (ils, 3.9, pypi, postgresql13, opensearch2)	13m 12s
Tests (ils, 3.9, pypi, postgresql14, opensearch2)	13m 23s
	1h 0m 31s

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