issue2551189 - increase size of words in full text index. Increased indexed word maxlength to 50 DB migration code is written and tests work. Restructured some tests to allow for code reuse. Docs. If this passes CI without errors 2551189 should be done. However, testing on my system generates errors. Encoding (indexer unicode russian unicode string invalid) and collation errors (utf8_bin not valid) when running under python2. No issues with python3 and I haven't changed code that should cause these since the last successful build in CI. So if this fails in CI we will have more checkins.

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