enh: bump version to 3.1.7 and update blob type to c_nchar in table creation

[huskar-t]

Description

enh: bump version to 3.1.7 and update blob type to c_nchar in table creation

Checklist

Please check the items in the checklist if applicable.

• Is the user manual updated?
• Are the test cases passed and automated?
• Is there no significant decrease in test coverage?

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.64%. Comparing base (15ee477) to head (aea41eb).

Additional details and impacted files

@@            Coverage Diff             @@
##              3.0     #116      +/-   ##
==========================================
+ Coverage   76.59%   76.64%   +0.05%     
==========================================
  Files         107      107              
  Lines        5494     5494              
  Branches      487      487              
==========================================
+ Hits         4208     4211       +3     
+ Misses       1143     1139       -4     
- Partials      143      144       +1     

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