[MBUILDCACHE-83] Allow to share cache configuration (maven-build-cache-config.xml) between projects

**[Réda Housni Alaoui](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=ralaoui)** opened **[MBUILDCACHE-83](https://issues.apache.org/jira/browse/MBUILDCACHE-83?redirect=false)** and commented

We have many maven projects that could benefit from this extension. They could share a common cache configuration.

Would it make sense to be able to pass an http url instead of a path to locate the configuration file to use? If yes, would it make sense to have a configuration merging algorithm between a remote configuration and a local configuration?

See https://github.com/apache/maven-build-cache-extension/blob/0410dc42c8fc3b7d06f982e2e46db41558e72145/src/main/java/org/apache/maven/buildcache/xml/CacheConfigImpl.java#L142 .

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No further details from [MBUILDCACHE-83](https://issues.apache.org/jira/browse/MBUILDCACHE-83?redirect=false)

Start at src/main/java/org/apache/maven/buildcache/xml/CacheConfigImpl.java around line 142, where the configuration path is handled. Investigate how configuration files are located and determine the requirements for HTTP URLs and merging remote and local configurations. Done requires an agreed design and implementation for shared configuration behavior, but the issue provides no tests or acceptance criteria.

Written by the indexing model from the issue text.