add ssl conn support to redis

[bobfantansy]

添加对Redis SSL连接支持。
sql_instance表中添加is_ssl字段，表明是否使用ssl进行连接。目前只支持redis

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (cdbd12e) 75.14% compared to head (11a0ac3) 75.14%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2215   +/-   ##
=======================================
  Coverage   75.14%   75.14%           
=======================================
  Files         105      105           
  Lines       15167    15169    +2     
=======================================
+ Hits        11397    11399    +2     
  Misses       3770     3770           

Impacted Files	Coverage Δ
sql/engines/redis.py	75.92% <ø> (ø)
sql/engines/__init__.py	66.34% <100.00%> (+0.32%)	⬆️
sql/models.py	96.58% <100.00%> (+<0.01%)	⬆️

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