feat: 添加挂载目录 baseDir 及 model名称 delegate 配置项

[songispm]

Checklist

• npm test passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

Affected core subsystem(s)

Description of change

[songispm]

支持 多个 client 配置不同 baseDir 与 delegate

[codecov]

Codecov Report

Merging #44 (65dee87) into master (123527c) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master       #44   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            6         5    -1     
  Lines           63        79   +16     
=========================================
+ Hits            63        79   +16     

Impacted Files	Coverage Δ
lib/mongoose.js	100.00% <100.00%> (ø)

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