feat: refactor TextAPI (cf. #50)

Feature

Summary

This MR moves most of the functionality out of tapi.xqm into separate designated modules. As a result, tapi.xqm mainly contains the RESTXQ endpoints.

In detail, the following modules have been created:

• tapi-collection.xqm: creating all information necessary for the TextAPI collection endpoint (/collection.json)
• tapi-manifest.xqm: creating all information necessary for the TextAPI collection endpoint (/manifest.json)
• tapi-item.xqm: creating all information necessary for the TextAPI collection endpoint (/latest/item.json)
• tapi-html.xqm: handling the creation of the HTML presentation of a given page (/content/xxxx.html)
• tapi-txt.xqm: handling the creation of the TXT presentation of a given page (/content/xxxx.txt) which is needed for the collation

All modules have been provided with extensive tests. The module functions and expected parameters aim to be descriptive to such a degree that additional documentation can be kept to a minimum (following Robert Martin's and Martin Fowler's advice).

---

Furthermore, several testsuites are considered and inspected during the unit_test stage of the CI/CD since every module of the ones mentioned above has its own unit testing module.

Compliance to “Definition of Done”

• Unit tests passed
• Code reviewed
• Acceptance criteria met
• Functional tests passed
• Non-Functional requirements met
• Product Owner accepts the User Story

Use Cases

As a developer, having clean and separate modules speeds up my work, and more tests assure my that everything is working fine.

Documentation

• I updated the README (if applicable)
• I provided my functions with appropriate documentation
• I updated existing documentation

Tests

Are we able to test this new feature?

• Yes, everything can be done via unit tests

Changelog

• I added a statement to the CHANGELOG.

Version number

• I bumped the version number in build.properties.

Related Tickets

#50 (closed), #57 (closed)

/cc Mathias Göbel, Frank Schneider, Michelle Weidling

CHANGELOG.md

@@ -13,6 +13,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 All further functionality has been moved to separate module and furnished with tests.
 - The test runner has been designed to be self-reporting, i.e. only faulty results are displayed fully.
 
+## [1.10.1] - 2020-09-24
+
+### Fixed
+
+- Faulty link to OpenAPI documentation of the RESTXQ endpoints has been corrected.
+
 ## [1.10.0] - 2020-09-18
 
 ### Added