[MGPG-137] Un-deprecate passphraseServerId

**[Lenny Primak](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=lprimak)** opened **[MGPG-137](https://issues.apache.org/jira/browse/MGPG-137?redirect=false)** and commented

IMHO this parameter has been deprecated in error.

It is used to referenced the "server" field in settings.xml, where passphrases are stored in an encrypted fashion. This is actually safer than setting clear-text passwords in environment variables in practice.

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**Affects:** 3.2.5

**Issue Links:**
- [MGPG-105](https://issues.apache.org/jira/browse/MGPG-105) Stop propagating bad practices; but allow for "compat mode"

Start by locating the handling and documentation for the passphraseServerId parameter in the Maven GPG plugin. Read the related compatibility behavior and issue MGPG-105 before determining the affected code and tests. Done means the parameter is no longer deprecated while preserving encrypted passphrase lookup through settings.xml.

Written by the indexing model from the issue text.