Defect/indexeswithoutsksincorrectindexes (#20)

* adding patch and create methods. both automatically add ConditionExpressions to either make sure the record exists before updating (patch) or make sure the record doesnt already exist (create)

* adding tests, not full working right now

* query had a defect preventing queries from being ran on tables without an sk. yikes.

* bumping version

* readme improvements

* when the primary pk and sk were part of a collection, scan did not correctly add the collection name to the key structure

* removing debug file and console log from test

* indexes without SKs would not have properly formatted keys. Before this commit, electro relied on the SK as the only means to segregate entities. With this change, if only an PK is present, the entity name will be place in the PK

src/entity.js

@@ -905,7 +905,7 @@ class Entity {
 	}
 
 	/* istanbul ignore next */
-	_getPrefixes({ collection = "", customFacets = {} } = {}) {
+	_getPrefixes({ collection = "", customFacets = {}, sk } = {}) {
 		/*
 			Collections will prefix the sort key so they can be queried with
 			a "begins_with" operator when crossing entities. It is also possible
@@ -933,6 +933,10 @@ class Entity {
 			keys.sk.prefix = this.model.prefixes.sk;
 		}
 
+		if (sk === undefined) {
+			keys.pk.prefix += keys.sk.prefix;	
+		}
+
 		if (customFacets.pk) {
 			keys.pk.prefix = "";
 			keys.pk.isCustom = customFacets.pk;
@@ -954,6 +958,7 @@ class Entity {
 		}
 		let facets = this.model.facets.byIndex[index];
 		let prefixes = this._getPrefixes(facets);
+		// let sk = [];
 		let pk = this._makeKey(
 			prefixes.pk.prefix,
 			facets.pk,
@@ -1121,6 +1126,9 @@ class Entity {
 			seenIndexes[indexName] = indexName;
 			let hasSk = !!index.sk;
 			let inCollection = !!index.collection;
+			if (!hasSk && inCollection) {
+				throw new Error(`Invalid index definition: Access pattern, ${accessPattern} ${indexName || "(PRIMARY INDEX)"}, contains a collection definition without a defined SK. Collections can only be defined on indexes with a defined SK.`);
+			}
 			let collection = index.collection || "";
 			let customFacets = {
 				pk: false,