feat: configurable GeoJSON coordinate precision (default 6)

[dkastl]

Closes #7.

Problem

GeoJSON output carried full floating-point precision (15-17 digits), e.g. 135.27597373034055. For EPSG:4326 that is far beyond any real-world accuracy (6 places ≈ 0.11 m, 7 ≈ 1 cm) and it bloats the payload, which is noticeable for large polygons. RGeo's GeoJSON encoder offers no precision option and upstream declines to add one (the original concern in #7), so the plugin now rounds coordinates itself.

Change

• Setting: new geojson_precision (default 6, clamped to 0..15) read via RedmineGtt.geojson_precision. Storage keeps full precision; only output is rounded, so nothing is lost.
• PostGIS path: ST_AsGeoJson(geom, <precision>) (the maxdecimaldigits argument). The precision is a clamped Integer, so the interpolation is injection-safe.
• RGeo path (Conversions::GeomToJson): rounds the numbers under each coordinates key after encoding, leaving properties untouched. This covers the map's issues-index GeoJSON, .geojson downloads, and single-feature output.
• Settings UI: a number field on the General tab, with en/ja/de strings.
• geodata_for_print (single-feature print, EPSG:3857 meters) is intentionally left as-is; it is a different unit and not the payload concern.

Verification

• Live in a Redmine 6.1 dev instance with a high-precision point: both the RGeo path (.geojson, .json) and the PostGIS path (index db_geojson) output [139.691701, 35.68953, 0.0] at the default; setting precision to 2 yields [139.69, 35.69] on both. Settings field renders and round-trips.
• Ruby tests pass (unit issue/project/user + API integration + gtt_map + filter API: 30 runs, 305 assertions, 0 failures).

Test note

assert_equal_coordinates previously compared at 5 decimals. Now that output is rounded to 6, comparing below the output precision double-rounds boundary values (e.g. 135.2528349 → round(6) 135.252835 → round(5) 135.25284, whereas a direct round(5) is 135.25283). The helper now compares at the output precision, and the "small geom changes" assertions use that rounding comparator instead of exact float equality.

[Copilot]

Pull request overview

Adds a configurable precision setting to round GeoJSON coordinates on output (default 6 decimals) to reduce payload size while preserving stored full-precision geometry, covering both the PostGIS (ST_AsGeoJson) and RGeo encoding paths.

Changes:

• Introduces RedmineGtt.geojson_precision with default/range clamping and a new plugin setting geojson_precision.
• Applies precision in the PostGIS select (ST_AsGeoJson(..., precision)) and rounds coordinates post-encode for the RGeo path.
• Updates settings UI and i18n strings; adjusts coordinate comparison helper/tests for the new output rounding behavior.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
lib/redmine_gtt.rb	Adds default/range constants and RedmineGtt.geojson_precision setting reader with clamping.
lib/redmine_gtt/patches/geojson_attribute.rb	Uses ST_AsGeoJson(..., precision) for DB-side GeoJSON generation.
lib/redmine_gtt/conversions.rb	Rounds numeric values under coordinates after RGeo GeoJSON encoding.
init.rb	Registers new plugin default setting geojson_precision: 6.
app/views/settings/gtt/_general.html.erb	Adds settings UI number field for GeoJSON precision (0–15).
config/locales/en.yml	Adds label/help text for the new setting (English).
config/locales/ja.yml	Adds label/help text for the new setting (Japanese).
config/locales/de.yml	Adds label/help text for the new setting (German).
test/test_helper.rb	Updates coordinate comparison helper to compare at output precision.
test/unit/issue_test.rb	Switches geom-change assertions to use the rounding-aware coordinate comparator.

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