docs(V5): document V5 API migration and add V5 signal documentation

Author: JavierMtzRdz

docs/api/README.md

@@ -6,6 +6,9 @@ nav_order: 4
 
 # Other Endpoints
 
+> **Active endpoints are part of the legacy V4 API, which is being phased out.** See the [V4 to V5 Migration Guide](v5_migration.md) for details on the Delphi V5 transition.
+{: .warning }
+
 This is the home of [Delphi](https://delphi.cmu.edu/)'s epidemiological data
 API for tracking infectious diseases such as influenza, dengue,
 and norovirus. Note that additional data, including most COVID-19 signals, is

docs/api/covidcast-signals/doctor-visits.md

@@ -5,6 +5,9 @@ grand_parent: Main Endpoint (COVIDcast)
 nav_order: 1
 ---
 
+> **Heads up:** This COVIDcast source is part of the legacy V4 API, which is being phased out. An actively maintained equivalent is available in V5 under the source `claims_data_outpatient`. See the [V4 to V5 Migration Guide](../v5_migration.md) for full details.
+{: .warning }
+
 # Doctor Visits
 {: .no_toc}
 

docs/api/covidcast-signals/hospital-admissions.md

@@ -5,6 +5,9 @@ grand_parent: Main Endpoint (COVIDcast)
 nav_order: 1
 ---
 
+> **Heads up:** This COVIDcast source is part of the legacy V4 API, which is being phased out. An actively maintained equivalent is available in V5 under the source `claims_data_inpatient`. See the [V4 to V5 Migration Guide](../v5_migration.md) for full details.
+{: .warning }
+
 # Hospital Admissions
 {: .no_toc}
 

docs/api/covidcast-signals/nchs-mortality.md

@@ -5,6 +5,9 @@ grand_parent: Main Endpoint (COVIDcast)
 nav_order: 1
 ---
 
+> **Heads up:** The legacy v4 Epidata API is being phased out. Check the [V4 to V5 Source Coverage](../v5_signals.md#v4-to-v5-source-coverage) table or query [`/epidata/v5/metadata/`](../v5_meta.md) directly (more up to date) for whether this source is available in V5 yet. See the [V4 to V5 Migration Guide](../v5_migration.md) for full details.
+{: .warning }
+
 # NCHS Mortality Data
 {: .no_toc}
 

docs/api/covidcast-signals/nhsn.md

@@ -4,6 +4,10 @@ parent: Data Sources and Signals
 grand_parent: Main Endpoint (COVIDcast)
 nav_order: 1
 ---
+
+> **Heads up:** This COVIDcast source is part of the legacy V4 API, which is being phased out. An actively maintained equivalent is available in V5 under the source `nhsn`. See the [V4 to V5 Migration Guide](../v5_migration.md) for full details.
+{: .warning }
+
 # National Healthcare Safety Network Respiratory Hospitalizations
 {: .no_toc}
 

docs/api/covidcast-signals/nssp.md

@@ -4,6 +4,10 @@ parent: Data Sources and Signals
 grand_parent: Main Endpoint (COVIDcast)
 nav_order: 1
 ---
+
+> **Heads up:** This COVIDcast source is part of the legacy V4 API, which is being phased out. An actively maintained equivalent is available in V5 under the source `nssp`. See the [V4 to V5 Migration Guide](../v5_migration.md) for full details.
+{: .warning }
+
 # National Syndromic Surveillance Program Emergency Department Visits
 {: .no_toc}
 

docs/api/covidcast-signals/quidel.md

@@ -5,6 +5,9 @@ grand_parent: Main Endpoint (COVIDcast)
 nav_order: 1
 ---
 
+> **Heads up:** The legacy v4 Epidata API is being phased out. Check the [V4 to V5 Source Coverage](../v5_signals.md#v4-to-v5-source-coverage) table or query [`/epidata/v5/metadata/`](../v5_meta.md) directly (more up to date) for whether this source is available in V5 yet. See the [V4 to V5 Migration Guide](../v5_migration.md) for full details.
+{: .warning }
+
 # Quidel
 {: .no_toc}
 

docs/api/covidcast.md

@@ -6,6 +6,9 @@ nav_order: 3
 
 # Main Epidata API
 
+> **This endpoint (`/epidata/covidcast/`) is part of the legacy V4 API, which is being phased out.** The legacy V4 API includes this endpoint. See the [V4 to V5 Migration Guide](v5_migration.md) for guidance on migrating your queries to the [Delphi V5 API](v5.md).
+{: .warning }
+
 This legacy Epidata API endpoint was formerly called COVIDcast.
 
 This is the documentation for accessing all Delphi's indicators via the `covidcast` endpoint of [Delphi](https://delphi.cmu.edu/)'s

docs/api/covidcast_meta.md

@@ -5,6 +5,9 @@ grand_parent: Main Endpoint (COVIDcast)
 nav_order: 0
 ---
 
+> **Heads up:** The legacy v4 Epidata API is being phased out. Please use the [V5 Metadata Discovery Endpoints](v5_meta.md) instead of this endpoint. See the [V4 to V5 Migration Guide](v5_migration.md) for full details.
+{: .warning }
+
 # COVIDcast Metadata
 
 The COVIDcast metadata endpoint (endpoint `covidcast_meta`) provides a list of all

docs/api/covidcast_signals.md

@@ -5,6 +5,10 @@ nav_order: 3
 has_children: true
 
 ---
+
+> **Heads up:** The legacy v4 Epidata API is being phased out. See the [V4 to V5 Migration Guide](v5_migration.md) and the [V4 to V5 Source Coverage](v5_signals.md#v4-to-v5-source-coverage) table for full details.
+{: .warning }
+
 # Delphi's COVID-19 Data Sources and Signals
 
 Delphi's COVID-19 Surveillance Streams data includes the following data sources.