add rss service (#117)

* add rss service

* git ignore rss

* update readme

* go fmt

* maintain map by url

* make rss service multi-tenant

rss/usage.md

@@ -0,0 +1,56 @@
+A single uniform API for crawling and indexing RSS feeds
+
+# RSS Service
+
+Designed to populate the posts service with RSS feeds from other blogs. Useful for migration or just to get outside content into the posts service.
+
+## Creating a feed
+
+### cURL
+
+```bash
+> curl 'https://api.m3o.com/rss/New' \
+  -H 'micro-namespace: $yourNamespace' \
+  -H 'authorization: Bearer $yourToken' \
+  -d '{"name":"a16z", "url": "http://a16z.com/feed/"}';
+{}
+```
+
+### CLI
+
+```shell
+micro rss add --name="a16z" --url=http://a16z.com/feed/
+```
+
+## Querying feeded posts
+
+```shell
+$ micro rss feed
+{
+	"entries": [
+		{
+			"id": "39cdfbd6e7534bcd868be9eebbf43f8f",
+			"title": "Anthony Albanese: From the NYSE to Crypto",
+			"slug": "anthony-albanese-from-the-nyse-to-crypto",
+			"created": "1605104742",
+			"updated": "1605105364",
+			"metadata": {
+				"domain": "a16z.com",
+				"link": "https://a16z.com/2020/10/28/anthony-albanese-from-the-nyse-to-crypto/"
+			}
+		},
+		{
+			"id": "5e9285c01311704e204322ba564cd99e",
+			"title": "Journal Club: From Insect Eyes to Nanomaterials",
+			"slug": "journal-club-from-insect-eyes-to-nanomaterials",
+			"created": "1605104741",
+			"updated": "1605105363",
+			"metadata": {
+				"domain": "a16z.com",
+				"link": "https://a16z.com/2020/10/29/journal-club-insect-eyes-nanomaterials/"
+			}
+		},
+	]
+}
+```
+