PLT-7302: Aggregate Elasticsearch indexes over a certain age. (#7224)

* PLT-7302: Aggregate Elasticsearch indexes over a certain age.

This is done by a scheduled daily job, in order to keep the shard count
to a sensible level in Elasticsearch.

* Use map[string]string instead of StringMap

i18n/en.json

@@ -3787,6 +3787,30 @@
     "id": "ent.compliance.run_started.info",
     "translation": "Compliance export started for job '{{.JobName}}' at '{{.FilePath}}'"
   },
+  {
+    "id": "ent.elasticsearch.aggregator_worker.get_indexes.error",
+    "translation": "Elasticsearch aggregator worker failed to get indexes"
+  },
+  {
+    "id": "ent.elasticsearch.aggregator_worker.create_index_job.error",
+    "translation": "Elasticsearch aggregator worker failed to create the indexing job"
+  },
+  {
+    "id": "ent.elasticsearch.aggregator_worker.delete_indexes.error",
+    "translation": "Elasticsearch aggregator worker failed to delete the indexes"
+  },
+  {
+    "id": "ent.elasticsearch.aggregator_worker.index_job_failed.error",
+    "translation": "Elasticsearch aggregator worker failed due to the indexing job failing"
+  },
+  {
+    "id": "ent.elasticsearch.indexer.do_job.parse_start_time.error",
+    "translation": "Elasticsearch indexing worker failed to parse the start time"
+  },
+  {
+    "id": "ent.elasticsearch.indexer.do_job.parse_end_time.error",
+    "translation": "Elasticsearch indexing worker failed to parse the end time"
+  },
   {
     "id": "ent.elasticsearch.create_client.connect_failed",
     "translation": "Setting up Elasticsearch Client Failed"
@@ -4435,6 +4459,14 @@
     "id": "model.config.is_valid.elastic_search.username.app_error",
     "translation": "Elastic Search Username setting must be provided when Elastic Search indexing is enabled."
   },
+  {
+    "id": "model.config.is_valid.elastic_search.aggregate_posts_after_days.app_error",
+    "translation": "Elasticsearch AggregatePostsAfterDays setting must be a number greater than or equal to 1"
+  },
+  {
+    "id": "model.config.is_valid.elastic_search.posts_aggregator_job_start_time.app_error",
+    "translation": "Elasticsearch PostsAggregatorJobStartTime setting must be a time in the format \"hh:mm\""
+  },
   {
     "id": "model.config.is_valid.email_batching_buffer_size.app_error",
     "translation": "Invalid email batching buffer size for email settings.  Must be zero or a positive number."