Fix Levenshtein distance algorithm

[avazirna]

Product Description

This PR fixes a small issue with the Levenshtein distance calculation, which was causing the fuzzy search to return false positives. For instance, the difference between aply into cape was previously 2 while it should be 3, and because our distance threshold is set at 2, the cape was a valid value for aply.

Another look to the source of the algorithm, I could also confirm that this was initially incorrect:

		// initial cost of skipping prefix in String s1
		newcost[0]=j-1;

and later on updated to the current form:

		// initial cost of skipping prefix in String s1
		newcost[0]=j;

Ticket: https://dimagi.atlassian.net/browse/SAAS-15738

Technical Summary

Safety Assurance

Automated test coverage

There are unit tests around this feature and they seem to have not been affected by this change.

Special deploy instructions

• This PR can be deployed after merge with no further considerations.

Rollback instructions

• This PR can be reverted after deploy with no further considerations.

Review

• The set of people pinged as reviewers is appropriate for the level of risk of the change.

Duplicate PR

Automatically duplicate this PR as defined in contributing.md.

[shubham1g5]

Looks good to me though can we write a unit test for the particular edge case we are trying to fix here.

[avazirna]

Duplicate PR

[avazirna]

duplicate this PR