Add `aggregate_temporal` openEO Process

[emmanuelmathot]

Objective

Implement the aggregate_temporal process in openEO by TiTiler.

Specification

• Process page: https://openeo.org/documentation/1.0/processes.html#aggregate_temporal
• JSON spec: https://github.com/Open-EO/openeo-processes/blob/master/aggregate_temporal.json

Implementation References

1. Raster Stack Data Model: https://sentinel-hub.github.io/titiler-openeo/raster-stack/

   • Understanding how temporal dimension is handled in TiTiler-openEO

2. Existing Implementation: aggregate_spatial in titiler/openeo/processes/implementations/spatial.py:L199

   • Follow similar patterns for parameter validation and callback handling

Implementation Steps

1. Copy specification

   • Download aggregate_temporal.json from openeo-processes repo
   • Place in data folder following existing process organization

2. Implement process

   • Parse temporal intervals (left-closed, right-open [start, end))
   • Handle RFC 3339 date-time strings and null values
   • Apply reducer callback to data within each interval
   • Handle temporal dimension per raster stack model

3. Register process

   • Add to process registry following existing patterns

4. Testing

   • Unit tests for various interval configurations
   • Test with different reducers (mean, median, min, max, sum)
   • Test with/without custom labels

Acceptance Criteria

• JSON spec copied to data folder
• Process implements specification correctly
• Works with standard reducer processes
• Includes tests
• Basic usage example