feat: extend NGSI-LD support for NGSIToPostgreSQL processor (and other global upgrades)

[bobeal]

Note: submitting the PR in draft status since there are still some things to finish (see TODOs below), but new features are already in good shape and tested on a real deployment.

Proposed changes

Globally extend the NGSI-LD support of the NGSIToPostgreSQL processor and also do some global upgrades (NiFi version, Java version):

• chore: upgrade NiFi version to 1.14.0 (only tested for NGSIToPostgreSQL processor)
• chore: set base Java version to 11 for nifi-ngsi-bundle
• chore: replace part of System.out statements by log statements
• feat: extract keys to ignore in payloads into a constant list for improved maintainability
• feat: add support for multi-attributes (section 4.5.5 of the NGSI-LD spec) to avoid too long (and truncated) names
  • a configurable prefix can be removed from the dataset ids
• feat: add support for sub-attributes of all types of attributes (was previously only supported for properties)
• feat: use types as much as possible for columns (e.g. TIMESTAMPTZ for dates or NUMERIC for numeric values)
  • currently using TEXT (default), TIMESTAMPTZ and NUMERIC (more could be added in the future)
  • it won't break existing installations because columns already exist, but they could benefit from such a new feature

TODOs before removing the draft status

• align NGSIv2 code where needed (e.g., in getValuesForInsert, listOfFields)
• add some specific tests for the new features
• upgrade bundle version (to which version?)

Types of changes

What types of changes does your code introduce to the project: Put an x in the boxes that apply

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist

• I have read the CONTRIBUTING doc
• I have signed the CLA
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)
• Any dependent changes have been merged and published in downstream modules

[bobeal]

I have read the CLA Document and I hereby sign the CLA