Route zstd compression config through EVCacheTranscoderProperties bundle (stacked on #197)

[joegoogle123]

Draft — stacked on top of #197. Merges in #196 and demonstrates the
reviewer's suggestion from #197 (comment) —
compression config can flow through EVCacheTranscoderProperties cleanly
without moving the codec out of EVCacheSerializingTranscoder.

Summary

Combines PR #196 (binary EVCacheValue serde + EVCacheTranscoderProperties
bundle) with PR #197 (zstd on EVCacheSerializingTranscoder) and replaces
PR #197's public setter-injection API with typed Property<T> handles owned
by the bundle.

What changes vs #197

• Removed setCompressionAlgorithmProperty and setCompressionLevelProperty
  from EVCacheSerializingTranscoder. Also removed the two mutable
  Property<T> fields those setters wrote to.
• Removed the redundant protected final String appName field on
  EVCacheSerializingTranscoder — single source of truth is
  properties.getAppName().
• Removed EVCacheTranscoder(String, PropertyRepository, ...) constructor
  overloads. Callers pass an EVCacheTranscoderProperties instead.
• Moved the CompressionAlgorithm enum from EVCacheSerializingTranscoder
  to EVCacheTranscoderProperties so the bundle can expose it as a typed
  return value.
• Normalized the compression-config Archaius keys from PR Add Zstd support for EVCache #197's
  evcacheclient.compression.* (Java source) to default.evcache.compression.*
  (matching PR Add Zstd support for EVCache #197's own PR description and the naming convention already
  used by default.evcache.max.data.size / default.evcache.compression.threshold).

The bundle now owns the compression config

New keys and defaults in EVCacheTranscoderProperties:

COMPRESSION_ALGORITHM   -> per-app: <app>.compression.algorithm
                          global:  default.evcache.compression.algorithm
                          default: CompressionAlgorithm.GZIP

COMPRESSION_ZSTD_LEVEL  -> per-app: <app>.compression.zstd.level
                          global:  default.evcache.compression.zstd.level
                          default: 3

The bundle stores two live Property<T> handles as final fields, resolved
once at construction:

private final Property<CompressionAlgorithm> compressionAlgorithmProperty;
private final Property<Integer>              zstdCompressionLevelProperty;

// in EVCacheTranscoderProperties ctor:
this.compressionAlgorithmProperty = getProperty(appName, propertyRepository,
        Key.COMPRESSION_ALGORITHM, String.class, DEFAULT_COMPRESSION_ALGORITHM.name())
        .map(s -> CompressionAlgorithm.valueOf(s.toUpperCase()));

this.zstdCompressionLevelProperty = getProperty(appName, propertyRepository,
        Key.COMPRESSION_ZSTD_LEVEL, Integer.class, DEFAULT_COMPRESSION_ZSTD_LEVEL);

public Property<CompressionAlgorithm> getCompressionAlgorithmProperty() {
    return compressionAlgorithmProperty;
}
public Property<Integer> getZstdCompressionLevelProperty() {
    return zstdCompressionLevelProperty;
}

The Property<CompressionAlgorithm> is built via Archaius's built-in
Property.map(Function<T, S>). .get() on the mapped handle re-parses the
underlying String on each call, so live FP updates propagate without JVM
restart and callers never see a stale enum. The upper-case wrap keeps the
FP case-insensitive.

EVCacheSerializingTranscoder.compress() becomes trivial

CompressionAlgorithm compressionAlgorithm = properties.getCompressionAlgorithmProperty().get();

switch (compressionAlgorithm) {
    case ZSTD:
        int zstdLevel = properties.getZstdCompressionLevelProperty().get();
        compressed = Zstd.compress(in, zstdLevel);
        break;
    case GZIP:
        compressed = super.compress(in);
        break;
    ...
}

No null-checks, no toUpperCase() + valueOf() boilerplate, no local field
plumbing.

Testing

./gradlew :evcache-core:test — BUILD SUCCESSFUL.

• EVCacheSerializingTranscoderTest (PR Add Zstd support for EVCache #197's suite): 22 tests pass,
  rewritten to build transcoders via
  new EVCacheTranscoderProperties(appName, repo) instead of the removed
  setters. Tests exercise all four combinations of {global, per-app} × {algo,
  level} keys plus cross-decode via magic-byte detection.
• EVCacheTranscoderPropertiesTest (PR EVCacheValue: opt-in compact binary serialization with backwards-compatible reads #196's suite): 15 tests pass.
• EVCacheValueSerdeTest (PR EVCacheValue: opt-in compact binary serialization with backwards-compatible reads #196's suite): 17 tests pass.

Dynamic-FP behavior end-to-end verified separately on a Spring Boot Netflix
sample app (via metatron curl -a gate POST /fastproperties/upsert and observed
propagation into the running JVM's REMOTE Archaius layer within ~30–45s).

Migration notes for downstream callers

PR #197 hasn't merged yet so the blast radius is small — the removed
setters have no external call sites. The renamed Archaius keys
(default.evcache.compression.* instead of evcacheclient.compression.*)
similarly can't be set in prod yet.

If a downstream caller of EVCacheTranscoder was passing
(appName, PropertyRepository) (only possible on PR #197's WIP branch),
replace with:

new EVCacheTranscoder(new EVCacheTranscoderProperties(appName, propertyRepository))

Compatibility

Public API on EVCacheSerializingTranscoder:

• Removed: setCompressionAlgorithmProperty(Property<String>),
  setCompressionLevelProperty(Property<Integer>).
• Added: EVCacheSerializingTranscoder(EVCacheTranscoderProperties, int).
• Kept: EVCacheSerializingTranscoder(), EVCacheSerializingTranscoder(int max).

Public API on EVCacheTranscoder:

• Removed: (String), (String, PropertyRepository), (String, int),
  (String, PropertyRepository, int), (String, int, int),
  (String, PropertyRepository, int, int) (all PR Add Zstd support for EVCache #197 additions).
• Added: EVCacheTranscoder(EVCacheTranscoderProperties).
• Kept: (), (int max), (int max, int compressionThreshold).

[janewang1680]

We should one instance of EVCacheTranscoderProperties per appName.