[Prostgres Vector Store] Add PGVector Driver option + Fix null character issue w/ TypeORM Driver (#3367)

* Add PGVector Driver option + Fix null character issue w/ TypeORM Driver

* Handle file upload case with PGVector

* Cleanup

* Fix data filtering for chatflow uploaded files

* Add distanceStrategy parameter

* Fix query to improve chatflow uploaded files filtering

* Ensure PGVector release connections

* Await client connected

* Make Postgres credentials optionnal when set on env variables

* Document env variables in nodes directories

* Prevent reuse client

* Fix empty metadataFilter

* Update CONTRIBUTING.md

* Update Postgres.ts

---------

Co-authored-by: Henry Heng <henryheng@flowiseai.com>

packages/components/nodes/vectorstores/Postgres/utils.ts

@@ -0,0 +1,21 @@
+import { defaultChain, INodeData } from '../../../src'
+
+export function getHost(nodeData?: INodeData) {
+    return defaultChain(nodeData?.inputs?.host, process.env.POSTGRES_VECTORSTORE_HOST)
+}
+
+export function getDatabase(nodeData?: INodeData) {
+    return defaultChain(nodeData?.inputs?.database, process.env.POSTGRES_VECTORSTORE_DATABASE)
+}
+
+export function getPort(nodeData?: INodeData) {
+    return defaultChain(nodeData?.inputs?.port, process.env.POSTGRES_VECTORSTORE_PORT, '5432')
+}
+
+export function getTableName(nodeData?: INodeData) {
+    return defaultChain(nodeData?.inputs?.tableName, process.env.POSTGRES_VECTORSTORE_TABLE_NAME, 'documents')
+}
+
+export function getContentColumnName(nodeData?: INodeData) {
+    return defaultChain(nodeData?.inputs?.contentColumnName, process.env.POSTGRES_VECTORSTORE_CONTENT_COLUMN_NAME, 'pageContent')
+}