新增配置项, enable_backup_switch, 允许工单提交人选择不备份

[LeoQuote]

如果不配置或配置关闭, 用户只能选择备份工单.

相关issue #198

[codecov]

Codecov Report

Merging #200 into master will increase coverage by 0.08%.
The diff coverage is 88.57%.

@@            Coverage Diff             @@
##           master     #200      +/-   ##
==========================================
+ Coverage   73.14%   73.23%   +0.08%     
==========================================
  Files          63       63              
  Lines        6979     7006      +27     
==========================================
+ Hits         5105     5131      +26     
- Misses       1874     1875       +1

Impacted Files	Coverage Δ
sql/views.py	41.84% <0%> (-0.23%)	⬇️
common/tests.py	100% <100%> (ø)	⬆️
sql/sql_workflow.py	62.65% <100%> (+0.45%)	⬆️
sql/tests.py	100% <100%> (ø)	⬆️
common/config.py	78.75% <81.81%> (+1.41%)	⬆️

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[LeoQuote]

错误文案特别拗口, 我写的是 不允许提交不备份工单 .

目前还没在config页面上增加这个配置项
中文显示预计为: 开启不备份选项(建议不开启, 强制要求备份)