Implement new xml schema version strategy

[copierrj]

Our xml schema files are versioned by having a version in the schema file url. Currently this version part of the url is also part of the filename in git.

We would like to remove the version from the filename in git and during the release procedure add the maven version to the schema file urls. This fixes the problem of having to change all references between schema files when changing the version.

Open issue: how to deal with the version attribute (= enum with previous versions).

relates to #915

[stephanr]

Proposal

All schemas are more or less structured like http://schemas.deegree.org/[grouping]/[version]/[name].xsd

The current schema situations have the following issues:

• Currently the Version Number is [Major].[Minor].[Increment] which would force everyone to rename all folders when the version should stay consistient
• Schema files are spitted on multiple modules which makes editing/renaming hard.
• Schema files are hard coded into the code (/META-INF/schemas/layers/feature/3.4.0/feature.xsd)
• Schema files contains import statements referencing complete URL to other schema files
  • http://schemas.deegree.org/layers/feature/3.4.0/feature.xsd
  • http://schemas.deegree.org/layers/base/3.4.0/base.xsd
• Hosting is capable of also provide HTTPs
• Version checking for every file is currently not active (as i see no references to org.deegree.services.controller.AbstractOWS.checkConfigVersion)
  it has been removed in 53fd059#diff-6cdeaab51250785e9f131927ea948a98
• Version Checking in org.deegree.services.controller.AbstractOWS.checkConfigVersion relies on hard coded versions which was only used for services
• org.deegree.services.wms.controller.WMSProvider

Proposal of changes made to the organisation of schema:

• The folder structure Schema files should be hosted on schemas.deegree.org has to be changed to:
  http://schemas.deegree.org/[major.minor.increment]/[grouping]/[name].xsd (static non modifiable)
  http://schemas.deegree.org/[major.minor]/[grouping]/[name].xsd (either as a symbolic link or replaced on every increment release)
• Generate a single artefact for each release (without version in path [grouping]/[name].xsd)
• Changes in schema made on increment version have to be compatible to minor versions
  Proposal of changes made to the configuration files:
• References are changed to only include major/minor version
• All schema files are changed to use only relative references to include/import (as the version number is not needed any more to build a correct relative address)
• Change the configVersion at the schema to be optional and of any type (backward compatibility)

Proposal of changes on Source-Code Level:

• Every file/folder has to drop the version directory
  From: /META-INF/schemas/layers/feature/3.4.0/feature.xsd
  To: /META-INF/schemas/layers/feature/feature.xsd
• Rename files (easy scriptable)
• Rename internal references
• Change the internal JAXB resolver (/uncoupled/deegree-jaxb-resolver/src/main/java/org/deegree/uncoupled/jaxb/CatalogResolver.java)
  to resolve http://schemas.deegree.org/[major.minor.increment] or http://schemas.deegree.org/[major.minor] to META-INF/schemas ignoring the exact version numbers
• Extend the JAXB Utility to make a check while loading the xml where the referenced schema files are checked if they use a version which is not matching the running deegree version

As this change will force the users to change their configuration files (for schema references) I propose to make minor increment release of deegree, even if I expect that the 3.4.x config files can be used expect for validation.

[stephanr]

For the last point of my proposal I prepared a proof of concept at the CodeSprint in Bucharest.
It is a routine used in the JAXB loading process to check xsi:schemaLocations for possible obsolete references.

Source: c838f5c

Log produced by JAXB loading:

[16:55:54]  INFO: [DefaultWorkspace] Preparing resource OWSProvider:samplewfs.
[16:55:55]  WARN: [SchemaVersionChecker]
[16:55:55]  WARN: [SchemaVersionChecker] *** Configuration uses an outdated Version please Upgrade refrence schemas.deegree.org/services/wfs/3.2.0/wfs_configuration.xsd
[16:55:55]  WARN: [SchemaVersionChecker]

Used configuration file samplewfs:

<deegreeWFS configVersion="3.4.0"
  xmlns="http://www.deegree.org/services/wfs"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.deegree.org/services/wfs
  http://schemas.deegree.org/services/wfs/3.2.0/wfs_configuration.xsd">
  <QueryCRS>urn:ogc:def:crs:EPSG::4258</QueryCRS>
</deegreeWFS>

[copierrj]

The TMC discussed this proposal in detail and is very happy about this development. We concluded that this would most likely result in resolving our configuration versioning issue.

[stephanr]

Done with #1335