[MRESOLVER-700] Bundle transport: read support

[cstamas]

This PR slightly improves the file transport to fully utilize FileSystem, which now can be ZipFileSystem as well. The "old" part remains unchanged.

For factory just added bundle: prefix, that now may be in form bundle:fileUri, where fileUri is basically a path of a ZIP file that must exist. The ZIP file is read only.

The point of this PR is that user can now use a "bundle" (see https://central.sonatype.org/publish/publish-portal-upload/) just like we did before with staging repositories. Various tools (njord?) can produce bundles. The ZIP file is "mounted" and artifacts from it becomes reachable to Maven just like from any remote repository.

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https://issues.apache.org/jira/browse/MRESOLVER-700

[slawekjaranowski]

Why bundle is read-only by default?

[cstamas]

Initial idea is really just to disseminate the idea that one can "mount" ZIP files as remote repositories. Like repository staging, and there, the main use case is usually to perform some sort of "testing" with newly baked artifacts. This PR makes Resolver able to consume these bundle ZIP files (essentially ZIP files containing artifacts laid down on remote repo layout) with all the metadata (maven metadata, checksums, signatures, etc).

[cstamas]

... aand after I commented, I think figured your point 😄 Yes, ultimately Resolver 2 could be used to create and read ZIP bundles. But, IMO we need to be very careful here, like we should allow "create from scratch" (like ZIP file is created from scratch) or "read created bundle", where you really just consume bundle for testing purposes. Existing ZIP bundle should not be modified, or at least, would be risky business.

Njord enforces this: it does not allow you to "export" to already existing ZIP files for example. But we should somewhere sit down and have a 🍻 that may be followed by a discussion about these things...

[cstamas]

For example we could achieve this by some extra params:

• by default (as in this PR) the ZIP file must exists and is read obly
• if URL has ?create=true QP, then Resolver could enforce ZIP file does not exists, and could make it read-write (and would become usable with altDeployRepository for example).

[cstamas]

Just one remark (somewhat related to this PR): While I worked on Njord 0.1.2 release, I figured that even if we allow bundle creation with Resolver (like the above mentioned ?create=true QP), the bundle would be usable for central publishing only, which is I think still fine. But for more advanced control and support, like bundle merging, validating for requirements, managing, etc you'd need advanced tools like Njord is. Also, this way created bundle would not be usable with Njord (lack of metadata). Still, this functionality would provide one single building block needed for Central Publishing: the ZIP bundle itself. But how user would publish it, etc, would NOT be solved.

[jira-importer]

Resolve #1435