refactor!: hydrator renamed to contextualizer

[dadrus]

This PR continues the series started with #370 and addresses #28.

The reason for this PR is that all Zero Trust papers are talking about contextualization of a request - adding more contextual information, which is not available in the request itself or in the information available about the authenticated subject. The name "hydrator", respectively the verb "hydration", which was so far used by heimdall for the same purpose, even if it talks about contextualization in the concept description, was misleading and not understood by many people.

Old:

# heimdall config (e.g. heimdall.yaml)

rules:
  mechanisms:
    # other mechanism definitions
    hydrators:
      - id: foo
        type: <specific type>
        config:
          <type specific config>
    #  other mechanism definitions

# rule file (e.g. rules.yaml)

- id: foo
  # other properties
  execute:
    # other mechanisms
    - hydrator: foo
    # other mechanisms

New:

# heimdall config (e.g. heimdall.yaml)

rules:
  mechanisms:
    # other mechanism definitions
    contextualizers:  # <-  changed
      - id: foo
        type: <specific type>
        config:
          <type specific config>
    #  other mechanism definitions

# rule file (e.g. rules.yaml)

- id: foo
  # other properties
  execute:
    # other mechanisms
    - contextualizer: foo   # <- changed
    # other mechanisms

[codecov]

Codecov Report

Merging #374 (11d5403) into main (4234e54) will increase coverage by 0.15%.
The diff coverage is 89.58%.

@@            Coverage Diff             @@
##             main     #374      +/-   ##
==========================================
+ Coverage   86.15%   86.31%   +0.15%     
==========================================
  Files         193      193              
  Lines        7750     7738      -12     
==========================================
+ Hits         6677     6679       +2     
+ Misses        914      903      -11     
+ Partials      159      156       -3     

Impacted Files	Coverage Δ
...rules/mechanisms/contextualizers/config_decoder.go	80.00% <ø> (ø)
internal/rules/rule_impl.go	90.00% <ø> (ø)
...chanisms/contextualizers/generic_contextualizer.go	85.89% <85.71%> (ø)
...ms/contextualizers/contextualizer_type_registry.go	87.50% <87.50%> (ø)
internal/rules/mechanisms/prototype_repository.go	77.00% <95.45%> (+1.21%)	⬆️
internal/rules/mechanisms/factory.go	100.00% <100.00%> (ø)
internal/rules/rule_factory.go	99.51% <100.00%> (ø)

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