Support "Active Directory Password" authentication method for TargetSqlConnectionAuthentication

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### This issue is for a: (mark with an `x`)
```
- [ ] bug report -> please search issues before submitting
- [x ] feature request
- [ ] documentation issue or request
- [ ] regression (a behavior that used to work and stopped in a new release)
```

### Minimal steps to reproduce
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For "SQL Server to Azure SQL Database" with Powershell, TargetSqlConnectionAuthentication currently only supports two types: The authentication type for connection, which can be either SqlAuthentication or WindowsAuthentication.

Can it be extended to support "Active Directory Password" or managed identity?

### Any log messages given by the failure
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### Expected/desired behavior
> "Active Directory Password" or managed identity authentication methods are supported.

### OS and Version?
> Windows 7, 8 or 10. Linux (which distribution). macOS (Yosemite? El Capitan? Sierra?)

### Versions
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### Mention any other details that might be useful

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> Thanks! We'll be in touch soon.

先定位 TargetSqlConnectionAuthentication，並檢視現有的 SqlAuthentication 和 WindowsAuthentication 選項是如何處理的。釐清目標是 Active Directory Password、managed identity，還是兩者；當選取的驗證方法可供 SQL Server 到 Azure SQL Database 的移轉接受，並能透過 PowerShell 流程運作時，即表示完成。

由索引模型根據 Issue 內容生成。